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	$64.51	12.188%	$72.3725	$72.37	$72.35	$72.40
Purchase #2	$67.72	7.261%	$72.6371	$72.64	$72.65	$72.60
Purchase #3	$53.65	10.488%	$59.2768	$59.28	$59.30	$59.30
Purchase #4	$190.98	3.281%	$197.2461	$197.25	$197.25	$197.20
Purchase #5	$226.72	4.270%	$236.4009	$236.40	$236.40	$236.40
Purchase #6	$34.74	7.204%	$37.2427	$37.24	$37.25	$37.20
Purchase #7	$22.65	3.326%	$23.4033	$23.40	$23.40	$23.40
7 purchase totals =	$660.97		$698.5794	$698.58	$698.60	$698.50