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	$199.75	10.723%	$221.1692	$221.17	$221.15	$221.20
Purchase #2	$111.75	6.355%	$118.8517	$118.85	$118.85	$118.90
Purchase #3	$120.93	12.844%	$136.4622	$136.46	$136.45	$136.50
Purchase #4	$199.43	10.585%	$220.5397	$220.54	$220.55	$220.50
Purchase #5	$216.37	8.603%	$234.9843	$234.98	$235.00	$235.00
Purchase #6	$59.84	3.171%	$61.7375	$61.74	$61.75	$61.70
Purchase #7	$102.69	8.749%	$111.6743	$111.67	$111.65	$111.70
7 purchase totals =	$1,010.76		$1,105.4189	$1,105.41	$1,105.40	$1,105.50