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	$145.65	11.329%	$162.1507	$162.15	$162.15	$162.20
Purchase #2	$34.61	13.816%	$39.3917	$39.39	$39.40	$39.40
Purchase #3	$152.63	12.817%	$172.1926	$172.19	$172.20	$172.20
Purchase #4	$228.34	13.820%	$259.8966	$259.90	$259.90	$259.90
Purchase #5	$238.96	4.343%	$249.338	$249.34	$249.35	$249.30
Purchase #6	$206.89	5.248%	$217.7476	$217.75	$217.75	$217.70
Purchase #7	$10.76	13.679%	$12.2319	$12.23	$12.25	$12.20
7 purchase totals =	$1,017.84		$1,112.9491	$1,112.95	$1,113.00	$1,112.90