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	$11.55	6.510%	$12.3019	$12.30	$12.30	$12.30
Purchase #2	$222.52	12.451%	$250.226	$250.23	$250.25	$250.20
Purchase #3	$114.27	9.713%	$125.369	$125.37	$125.35	$125.40
Purchase #4	$214.65	3.664%	$222.5148	$222.51	$222.50	$222.50
Purchase #5	$216.35	13.619%	$245.8147	$245.81	$245.80	$245.80
Purchase #6	$182.79	12.185%	$205.063	$205.06	$205.05	$205.10
Purchase #7	$92.98	10.814%	$103.0349	$103.03	$103.05	$103.00
7 purchase totals =	$1,055.11		$1,164.3243	$1,164.31	$1,164.30	$1,164.30