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	$111.74	11.857%	$124.989	$124.99	$125.00	$125.00
Purchase #2	$24.40	8.610%	$26.5008	$26.50	$26.50	$26.50
Purchase #3	$142.51	5.594%	$150.482	$150.48	$150.50	$150.50
Purchase #4	$212.44	5.156%	$223.3934	$223.39	$223.40	$223.40
Purchase #5	$108.60	3.648%	$112.5617	$112.56	$112.55	$112.60
Purchase #6	$225.89	10.538%	$249.6943	$249.69	$249.70	$249.70
Purchase #7	$230.46	10.315%	$254.2319	$254.23	$254.25	$254.20
7 purchase totals =	$1,056.04		$1,141.8531	$1,141.84	$1,141.90	$1,141.90