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	$250.92	5.398%	$264.4647	$264.46	$264.45	$264.50
Purchase #2	$77.58	6.173%	$82.369	$82.37	$82.35	$82.40
Purchase #3	$106.51	11.183%	$118.421	$118.42	$118.40	$118.40
Purchase #4	$231.57	4.355%	$241.6549	$241.65	$241.65	$241.70
Purchase #5	$208.66	6.734%	$222.7112	$222.71	$222.70	$222.70
Purchase #6	$157.40	6.867%	$168.2087	$168.21	$168.20	$168.20
Purchase #7	$105.85	9.634%	$116.0476	$116.05	$116.05	$116.00
7 purchase totals =	$1,138.49		$1,213.8771	$1,213.87	$1,213.80	$1,213.90