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	$221.84	6.340%	$235.9047	$235.90	$235.90	$235.90
Purchase #2	$187.73	11.725%	$209.7413	$209.74	$209.75	$209.70
Purchase #3	$167.50	3.478%	$173.3257	$173.33	$173.35	$173.30
Purchase #4	$171.45	13.506%	$194.606	$194.61	$194.60	$194.60
Purchase #5	$139.99	13.377%	$158.7165	$158.72	$158.70	$158.70
Purchase #6	$28.72	12.453%	$32.2965	$32.30	$32.30	$32.30
Purchase #7	$44.29	3.734%	$45.9438	$45.94	$45.95	$45.90
7 purchase totals =	$961.52		$1,050.5345	$1,050.54	$1,050.55	$1,050.40