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	$130.42	7.871%	$140.6854	$140.69	$140.70	$140.70
Purchase #2	$139.42	3.637%	$144.4907	$144.49	$144.50	$144.50
Purchase #3	$231.44	5.398%	$243.9331	$243.93	$243.95	$243.90
Purchase #4	$13.35	13.652%	$15.1725	$15.17	$15.15	$15.20
Purchase #5	$250.85	5.437%	$264.4887	$264.49	$264.50	$264.50
Purchase #6	$209.27	6.213%	$222.2719	$222.27	$222.25	$222.30
Purchase #7	$138.57	7.178%	$148.5166	$148.52	$148.50	$148.50
7 purchase totals =	$1,113.32		$1,179.5589	$1,179.56	$1,179.55	$1,179.60