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	$75.59	8.847%	$82.2774	$82.28	$82.30	$82.30
Purchase #2	$208.49	11.850%	$233.1961	$233.20	$233.20	$233.20
Purchase #3	$130.87	9.364%	$143.1247	$143.12	$143.10	$143.10
Purchase #4	$150.50	10.446%	$166.2212	$166.22	$166.20	$166.20
Purchase #5	$98.39	7.808%	$106.0723	$106.07	$106.05	$106.10
Purchase #6	$241.50	10.414%	$266.6498	$266.65	$266.65	$266.60
Purchase #7	$90.79	6.719%	$96.8902	$96.89	$96.90	$96.90
7 purchase totals =	$996.13		$1,094.4317	$1,094.43	$1,094.40	$1,094.40