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	$145.74	10.113%	$160.4787	$160.48	$160.50	$160.50
Purchase #2	$65.48	7.150%	$70.1618	$70.16	$70.15	$70.20
Purchase #3	$119.37	7.643%	$128.4934	$128.49	$128.50	$128.50
Purchase #4	$57.57	11.586%	$64.2401	$64.24	$64.25	$64.20
Purchase #5	$139.58	10.193%	$153.8074	$153.81	$153.80	$153.80
Purchase #6	$64.86	9.642%	$71.1138	$71.11	$71.10	$71.10
Purchase #7	$57.93	11.221%	$64.4303	$64.43	$64.45	$64.40
7 purchase totals =	$650.53		$712.7255	$712.72	$712.75	$712.70