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	$52.58	6.232%	$55.8568	$55.86	$55.85	$55.90
Purchase #2	$10.57	4.393%	$11.0343	$11.03	$11.05	$11.00
Purchase #3	$123.86	10.700%	$137.113	$137.11	$137.10	$137.10
Purchase #4	$27.95	10.751%	$30.9549	$30.95	$30.95	$31.00
Purchase #5	$173.85	9.216%	$189.872	$189.87	$189.85	$189.90
Purchase #6	$205.28	9.103%	$223.9666	$223.97	$223.95	$224.00
Purchase #7	$111.64	10.817%	$123.7161	$123.72	$123.70	$123.70
7 purchase totals =	$705.73		$772.5137	$772.51	$772.45	$772.60