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	$196.71	10.410%	$217.1875	$217.19	$217.20	$217.20
Purchase #2	$52.54	4.464%	$54.8854	$54.89	$54.90	$54.90
Purchase #3	$46.90	8.352%	$50.8171	$50.82	$50.80	$50.80
Purchase #4	$99.45	5.708%	$105.1266	$105.13	$105.15	$105.10
Purchase #5	$22.42	8.110%	$24.2383	$24.24	$24.25	$24.20
Purchase #6	$201.55	10.499%	$222.7107	$222.71	$222.70	$222.70
Purchase #7	$126.60	12.509%	$142.4364	$142.44	$142.45	$142.40
7 purchase totals =	$746.17		$817.4020	$817.42	$817.45	$817.30