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	$104.45	5.270%	$109.9545	$109.95	$109.95	$110.00
Purchase #2	$231.57	10.675%	$256.2901	$256.29	$256.30	$256.30
Purchase #3	$39.49	7.691%	$42.5272	$42.53	$42.55	$42.50
Purchase #4	$190.80	3.381%	$197.2509	$197.25	$197.25	$197.30
Purchase #5	$204.71	3.752%	$212.3907	$212.39	$212.40	$212.40
Purchase #6	$156.62	10.659%	$173.3141	$173.31	$173.30	$173.30
Purchase #7	$51.89	7.377%	$55.7179	$55.72	$55.70	$55.70
7 purchase totals =	$979.53		$1,047.4454	$1,047.44	$1,047.45	$1,047.50