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	$53.90	4.364%	$56.2522	$56.25	$56.25	$56.30
Purchase #2	$120.33	11.721%	$134.4339	$134.43	$134.45	$134.40
Purchase #3	$36.79	12.674%	$41.4528	$41.45	$41.45	$41.50
Purchase #4	$39.51	9.461%	$43.248	$43.25	$43.25	$43.20
Purchase #5	$97.63	7.691%	$105.1387	$105.14	$105.15	$105.10
Purchase #6	$70.62	12.556%	$79.487	$79.49	$79.50	$79.50
Purchase #7	$195.39	10.451%	$215.8102	$215.81	$215.80	$215.80
7 purchase totals =	$614.17		$675.8228	$675.82	$675.85	$675.80