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	$210.39	9.308%	$229.9731	$229.97	$229.95	$230.00
Purchase #2	$82.86	9.690%	$90.8891	$90.89	$90.90	$90.90
Purchase #3	$58.55	11.415%	$65.2335	$65.23	$65.25	$65.20
Purchase #4	$83.29	7.198%	$89.2852	$89.29	$89.30	$89.30
Purchase #5	$16.41	9.773%	$18.0137	$18.01	$18.00	$18.00
Purchase #6	$243.85	7.744%	$262.7337	$262.73	$262.75	$262.70
Purchase #7	$155.28	13.281%	$175.9027	$175.90	$175.90	$175.90
7 purchase totals =	$850.63		$932.0310	$932.02	$932.05	$932.00