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	$226.36	13.169%	$256.1693	$256.17	$256.15	$256.20
Purchase #2	$169.62	3.416%	$175.4142	$175.41	$175.40	$175.40
Purchase #3	$36.55	3.215%	$37.7251	$37.73	$37.75	$37.70
Purchase #4	$85.91	4.418%	$89.7055	$89.71	$89.70	$89.70
Purchase #5	$48.30	8.818%	$52.5591	$52.56	$52.55	$52.60
Purchase #6	$223.48	4.552%	$233.6528	$233.65	$233.65	$233.70
Purchase #7	$86.28	13.451%	$97.8855	$97.89	$97.90	$97.90
7 purchase totals =	$876.50		$943.1115	$943.12	$943.10	$943.20