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	$50.47	5.573%	$53.2827	$53.28	$53.30	$53.30
Purchase #2	$35.29	5.333%	$37.172	$37.17	$37.15	$37.20
Purchase #3	$111.56	5.381%	$117.563	$117.56	$117.55	$117.60
Purchase #4	$112.50	11.331%	$125.2474	$125.25	$125.25	$125.20
Purchase #5	$66.45	9.387%	$72.6877	$72.69	$72.70	$72.70
Purchase #6	$181.67	5.486%	$191.6364	$191.64	$191.65	$191.60
Purchase #7	$53.45	9.306%	$58.4241	$58.42	$58.40	$58.40
7 purchase totals =	$611.39		$656.0133	$656.01	$656.00	$656.00