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	$141.95	9.842%	$155.9207	$155.92	$155.90	$155.90
Purchase #2	$244.73	12.700%	$275.8107	$275.81	$275.80	$275.80
Purchase #3	$244.97	4.272%	$255.4351	$255.44	$255.45	$255.40
Purchase #4	$73.83	10.495%	$81.5785	$81.58	$81.60	$81.60
Purchase #5	$99.66	9.776%	$109.4028	$109.40	$109.40	$109.40
Purchase #6	$80.81	13.866%	$92.0151	$92.02	$92.00	$92.00
Purchase #7	$186.86	9.267%	$204.1763	$204.18	$204.20	$204.20
7 purchase totals =	$1,072.81		$1,174.3392	$1,174.35	$1,174.35	$1,174.30