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	$147.55	8.121%	$159.5325	$159.53	$159.55	$159.50
Purchase #2	$78.52	13.372%	$89.0197	$89.02	$89.00	$89.00
Purchase #3	$40.86	12.369%	$45.914	$45.91	$45.90	$45.90
Purchase #4	$62.62	5.180%	$65.8637	$65.86	$65.85	$65.90
Purchase #5	$195.39	4.369%	$203.9266	$203.93	$203.95	$203.90
Purchase #6	$202.69	5.646%	$214.1339	$214.13	$214.15	$214.10
Purchase #7	$82.87	12.219%	$92.9959	$93.00	$93.00	$93.00
7 purchase totals =	$810.50		$871.3863	$871.38	$871.40	$871.30