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	$188.89	11.561%	$210.7276	$210.73	$210.75	$210.70
Purchase #2	$80.28	8.194%	$86.8581	$86.86	$86.85	$86.90
Purchase #3	$88.84	13.175%	$100.5447	$100.54	$100.55	$100.50
Purchase #4	$112.31	7.770%	$121.0365	$121.04	$121.05	$121.00
Purchase #5	$208.70	6.550%	$222.3699	$222.37	$222.35	$222.40
Purchase #6	$173.77	8.673%	$188.8411	$188.84	$188.85	$188.80
Purchase #7	$130.31	9.675%	$142.9175	$142.92	$142.90	$142.90
7 purchase totals =	$983.10		$1,073.2954	$1,073.30	$1,073.30	$1,073.20