Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.25	10.602%	$131.8929	$131.89	$131.90	$131.90
Purchase #2	$203.25	9.697%	$222.9592	$222.96	$222.95	$223.00
Purchase #3	$237.53	11.622%	$265.1357	$265.14	$265.15	$265.10
Purchase #4	$128.88	3.465%	$133.3457	$133.35	$133.35	$133.30
Purchase #5	$152.71	9.760%	$167.6145	$167.61	$167.60	$167.60
Purchase #6	$170.46	11.707%	$190.4158	$190.42	$190.40	$190.40
Purchase #7	$101.67	11.384%	$113.2441	$113.24	$113.25	$113.20
7 purchase totals =	$1,113.75		$1,224.6079	$1,224.61	$1,224.60	$1,224.50