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	$108.25	6.499%	$115.2852	$115.29	$115.30	$115.30
Purchase #2	$99.80	10.110%	$109.8898	$109.89	$109.90	$109.90
Purchase #3	$71.73	12.845%	$80.9437	$80.94	$80.95	$80.90
Purchase #4	$212.44	4.728%	$222.4842	$222.48	$222.50	$222.50
Purchase #5	$189.49	3.180%	$195.5158	$195.52	$195.50	$195.50
Purchase #6	$188.81	11.441%	$210.4118	$210.41	$210.40	$210.40
Purchase #7	$167.56	6.868%	$179.068	$179.07	$179.05	$179.10
7 purchase totals =	$1,038.08		$1,113.5985	$1,113.60	$1,113.60	$1,113.60