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	$183.53	4.246%	$191.3227	$191.32	$191.30	$191.30
Purchase #2	$196.47	12.824%	$221.6653	$221.67	$221.65	$221.70
Purchase #3	$217.45	10.556%	$240.404	$240.40	$240.40	$240.40
Purchase #4	$165.52	4.564%	$173.0743	$173.07	$173.05	$173.10
Purchase #5	$162.65	11.571%	$181.4702	$181.47	$181.45	$181.50
Purchase #6	$104.75	9.788%	$115.0029	$115.00	$115.00	$115.00
Purchase #7	$233.86	10.546%	$258.5229	$258.52	$258.50	$258.50
7 purchase totals =	$1,264.23		$1,381.4623	$1,381.45	$1,381.35	$1,381.50