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	$189.72	3.699%	$196.7377	$196.74	$196.75	$196.70
Purchase #2	$133.91	5.381%	$141.1157	$141.12	$141.10	$141.10
Purchase #3	$117.74	3.598%	$121.9763	$121.98	$122.00	$122.00
Purchase #4	$116.69	11.634%	$130.2657	$130.27	$130.25	$130.30
Purchase #5	$81.37	11.742%	$90.9245	$90.92	$90.90	$90.90
Purchase #6	$245.32	8.136%	$265.2792	$265.28	$265.30	$265.30
Purchase #7	$206.52	8.305%	$223.6715	$223.67	$223.65	$223.70
7 purchase totals =	$1,091.27		$1,169.9706	$1,169.98	$1,169.95	$1,170.00