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	$105.71	11.576%	$117.947	$117.95	$117.95	$117.90
Purchase #2	$108.73	5.479%	$114.6873	$114.69	$114.70	$114.70
Purchase #3	$92.61	7.413%	$99.4752	$99.48	$99.50	$99.50
Purchase #4	$239.75	4.421%	$250.3493	$250.35	$250.35	$250.30
Purchase #5	$137.47	13.650%	$156.2347	$156.23	$156.25	$156.20
Purchase #6	$170.96	8.646%	$185.7412	$185.74	$185.75	$185.70
Purchase #7	$157.39	11.270%	$175.1279	$175.13	$175.15	$175.10
7 purchase totals =	$1,012.62		$1,099.5626	$1,099.57	$1,099.65	$1,099.40