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	$185.88	7.711%	$200.2132	$200.21	$200.20	$200.20
Purchase #2	$127.25	10.365%	$140.4395	$140.44	$140.45	$140.40
Purchase #3	$53.31	4.749%	$55.8417	$55.84	$55.85	$55.80
Purchase #4	$30.98	4.109%	$32.253	$32.25	$32.25	$32.30
Purchase #5	$85.90	4.432%	$89.7071	$89.71	$89.70	$89.70
Purchase #6	$124.81	6.581%	$133.0237	$133.02	$133.00	$133.00
Purchase #7	$204.45	4.429%	$213.5051	$213.51	$213.50	$213.50
7 purchase totals =	$812.58		$864.9833	$864.98	$864.95	$864.90