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	$236.83	9.576%	$259.5088	$259.51	$259.50	$259.50
Purchase #2	$21.74	4.427%	$22.7024	$22.70	$22.70	$22.70
Purchase #3	$156.74	8.696%	$170.3701	$170.37	$170.35	$170.40
Purchase #4	$222.43	3.525%	$230.2707	$230.27	$230.25	$230.30
Purchase #5	$234.41	10.814%	$259.7591	$259.76	$259.75	$259.80
Purchase #6	$188.40	6.375%	$200.4105	$200.41	$200.40	$200.40
Purchase #7	$38.77	9.107%	$42.3008	$42.30	$42.30	$42.30
7 purchase totals =	$1,099.32		$1,185.3224	$1,185.32	$1,185.25	$1,185.40