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	$106.78	4.399%	$111.4773	$111.48	$111.50	$111.50
Purchase #2	$74.56	11.250%	$82.948	$82.95	$82.95	$82.90
Purchase #3	$198.43	10.226%	$218.7215	$218.72	$218.70	$218.70
Purchase #4	$5.79	8.499%	$6.2821	$6.28	$6.30	$6.30
Purchase #5	$183.95	3.439%	$190.276	$190.28	$190.30	$190.30
Purchase #6	$16.74	6.751%	$17.8701	$17.87	$17.85	$17.90
Purchase #7	$41.55	5.206%	$43.7131	$43.71	$43.70	$43.70
7 purchase totals =	$627.80		$671.2881	$671.29	$671.30	$671.30