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	$53.82	3.772%	$55.8501	$55.85	$55.85	$55.90
Purchase #2	$23.57	10.767%	$26.1078	$26.11	$26.10	$26.10
Purchase #3	$87.96	7.693%	$94.7268	$94.73	$94.75	$94.70
Purchase #4	$49.70	7.413%	$53.3843	$53.38	$53.40	$53.40
Purchase #5	$12.38	5.148%	$13.0173	$13.02	$13.00	$13.00
Purchase #6	$56.79	4.375%	$59.2746	$59.27	$59.25	$59.30
Purchase #7	$211.67	10.255%	$233.3768	$233.38	$233.40	$233.40
7 purchase totals =	$495.89		$535.7377	$535.74	$535.75	$535.80