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	$204.76	3.807%	$212.5552	$212.56	$212.55	$212.60
Purchase #2	$83.74	6.728%	$89.374	$89.37	$89.35	$89.40
Purchase #3	$134.76	12.689%	$151.8597	$151.86	$151.85	$151.90
Purchase #4	$146.34	7.333%	$157.0711	$157.07	$157.05	$157.10
Purchase #5	$67.83	7.164%	$72.6893	$72.69	$72.70	$72.70
Purchase #6	$97.85	8.170%	$105.8443	$105.84	$105.85	$105.80
Purchase #7	$53.34	9.299%	$58.3001	$58.30	$58.30	$58.30
7 purchase totals =	$788.62		$847.6937	$847.69	$847.65	$847.80