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	$166.82	11.564%	$186.1111	$186.11	$186.10	$186.10
Purchase #2	$238.28	7.584%	$256.3512	$256.35	$256.35	$256.40
Purchase #3	$182.73	9.214%	$199.5667	$199.57	$199.55	$199.60
Purchase #4	$74.43	10.808%	$82.4744	$82.47	$82.45	$82.50
Purchase #5	$240.50	8.547%	$261.0555	$261.06	$261.05	$261.10
Purchase #6	$5.47	7.527%	$5.8817	$5.88	$5.90	$5.90
Purchase #7	$148.67	7.824%	$160.3019	$160.30	$160.30	$160.30
7 purchase totals =	$1,056.90		$1,151.7425	$1,151.74	$1,151.70	$1,151.90