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	$26.48	11.774%	$29.5978	$29.60	$29.60	$29.60
Purchase #2	$208.73	6.258%	$221.7923	$221.79	$221.80	$221.80
Purchase #3	$44.77	13.640%	$50.8766	$50.88	$50.90	$50.90
Purchase #4	$73.33	8.399%	$79.489	$79.49	$79.50	$79.50
Purchase #5	$91.91	9.550%	$100.6874	$100.69	$100.70	$100.70
Purchase #6	$177.63	10.403%	$196.1088	$196.11	$196.10	$196.10
Purchase #7	$226.83	12.723%	$255.6896	$255.69	$255.70	$255.70
7 purchase totals =	$849.68		$934.2415	$934.25	$934.30	$934.30