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	$109.59	11.518%	$122.2126	$122.21	$122.20	$122.20
Purchase #2	$153.86	8.651%	$167.1704	$167.17	$167.15	$167.20
Purchase #3	$56.36	9.112%	$61.4955	$61.50	$61.50	$61.50
Purchase #4	$249.71	5.848%	$264.313	$264.31	$264.30	$264.30
Purchase #5	$234.60	8.152%	$253.7246	$253.72	$253.70	$253.70
Purchase #6	$70.48	3.427%	$72.8953	$72.90	$72.90	$72.90
Purchase #7	$240.46	11.733%	$268.6732	$268.67	$268.65	$268.70
7 purchase totals =	$1,115.06		$1,210.4846	$1,210.48	$1,210.40	$1,210.50