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	$222.89	12.600%	$250.9741	$250.97	$250.95	$251.00
Purchase #2	$6.88	10.719%	$7.6175	$7.62	$7.60	$7.60
Purchase #3	$198.94	11.819%	$222.4527	$222.45	$222.45	$222.50
Purchase #4	$233.86	13.274%	$264.9026	$264.90	$264.90	$264.90
Purchase #5	$152.40	4.161%	$158.7414	$158.74	$158.75	$158.70
Purchase #6	$123.41	5.432%	$130.1136	$130.11	$130.10	$130.10
Purchase #7	$213.40	11.763%	$238.5022	$238.50	$238.50	$238.50
7 purchase totals =	$1,151.78		$1,273.3041	$1,273.29	$1,273.25	$1,273.30