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	$127.92	10.301%	$141.097	$141.10	$141.10	$141.10
Purchase #2	$174.50	3.411%	$180.4522	$180.45	$180.45	$180.50
Purchase #3	$230.98	10.749%	$255.808	$255.81	$255.80	$255.80
Purchase #4	$247.74	8.240%	$268.1538	$268.15	$268.15	$268.20
Purchase #5	$97.64	8.165%	$105.6123	$105.61	$105.60	$105.60
Purchase #6	$114.57	8.127%	$123.8811	$123.88	$123.90	$123.90
Purchase #7	$157.88	12.776%	$178.0507	$178.05	$178.05	$178.10
7 purchase totals =	$1,151.23		$1,253.0551	$1,253.05	$1,253.05	$1,253.20