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	$150.40	7.443%	$161.5943	$161.59	$161.60	$161.60
Purchase #2	$37.31	5.869%	$39.4997	$39.50	$39.50	$39.50
Purchase #3	$105.75	4.782%	$110.807	$110.81	$110.80	$110.80
Purchase #4	$101.92	3.580%	$105.5687	$105.57	$105.55	$105.60
Purchase #5	$99.66	12.240%	$111.8584	$111.86	$111.85	$111.90
Purchase #6	$229.63	4.480%	$239.9174	$239.92	$239.90	$239.90
Purchase #7	$97.82	6.681%	$104.3554	$104.36	$104.35	$104.40
7 purchase totals =	$822.49		$873.6009	$873.61	$873.55	$873.70