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	$89.87	7.767%	$96.8502	$96.85	$96.85	$96.90
Purchase #2	$57.78	13.730%	$65.7132	$65.71	$65.70	$65.70
Purchase #3	$30.85	4.844%	$32.3444	$32.34	$32.35	$32.30
Purchase #4	$56.38	9.765%	$61.8855	$61.89	$61.90	$61.90
Purchase #5	$53.33	3.573%	$55.2355	$55.24	$55.25	$55.20
Purchase #6	$59.72	13.452%	$67.7535	$67.75	$67.75	$67.80
Purchase #7	$203.62	9.872%	$223.7214	$223.72	$223.70	$223.70
7 purchase totals =	$551.55		$603.5037	$603.50	$603.50	$603.50