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	$94.56	6.319%	$100.5352	$100.54	$100.55	$100.50
Purchase #2	$167.47	4.102%	$174.3396	$174.34	$174.35	$174.30
Purchase #3	$77.28	7.103%	$82.7692	$82.77	$82.75	$82.80
Purchase #4	$166.89	10.820%	$184.9475	$184.95	$184.95	$184.90
Purchase #5	$120.92	3.569%	$125.2356	$125.24	$125.25	$125.20
Purchase #6	$191.73	10.873%	$212.5768	$212.58	$212.60	$212.60
Purchase #7	$53.62	5.590%	$56.6174	$56.62	$56.60	$56.60
7 purchase totals =	$872.47		$937.0213	$937.04	$937.05	$936.90