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	$199.53	8.824%	$217.1365	$217.14	$217.15	$217.10
Purchase #2	$94.98	12.354%	$106.7138	$106.71	$106.70	$106.70
Purchase #3	$191.33	5.285%	$201.4418	$201.44	$201.45	$201.40
Purchase #4	$118.46	4.132%	$123.3548	$123.35	$123.35	$123.40
Purchase #5	$162.27	6.384%	$172.6293	$172.63	$172.65	$172.60
Purchase #6	$107.77	3.243%	$111.265	$111.27	$111.25	$111.30
Purchase #7	$134.32	4.612%	$140.5148	$140.51	$140.50	$140.50
7 purchase totals =	$1,008.66		$1,073.0560	$1,073.05	$1,073.05	$1,073.00