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	$88.90	5.250%	$93.5673	$93.57	$93.55	$93.60
Purchase #2	$170.77	4.328%	$178.1609	$178.16	$178.15	$178.20
Purchase #3	$99.42	12.304%	$111.6526	$111.65	$111.65	$111.70
Purchase #4	$158.95	7.568%	$170.9793	$170.98	$171.00	$171.00
Purchase #5	$54.33	10.171%	$59.8559	$59.86	$59.85	$59.90
Purchase #6	$171.94	11.301%	$191.3709	$191.37	$191.35	$191.40
Purchase #7	$92.83	6.324%	$98.7006	$98.70	$98.70	$98.70
7 purchase totals =	$837.14		$904.2875	$904.29	$904.25	$904.50