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	$242.73	5.237%	$255.4418	$255.44	$255.45	$255.40
Purchase #2	$223.25	7.676%	$240.3867	$240.39	$240.40	$240.40
Purchase #3	$91.77	5.654%	$96.9587	$96.96	$96.95	$97.00
Purchase #4	$149.56	13.750%	$170.1245	$170.12	$170.10	$170.10
Purchase #5	$176.93	4.127%	$184.2319	$184.23	$184.25	$184.20
Purchase #6	$94.62	9.338%	$103.4556	$103.46	$103.45	$103.50
Purchase #7	$75.40	3.299%	$77.8874	$77.89	$77.90	$77.90
7 purchase totals =	$1,054.26		$1,128.4866	$1,128.49	$1,128.50	$1,128.50