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	$165.94	11.796%	$185.5143	$185.51	$185.50	$185.50
Purchase #2	$83.59	3.657%	$86.6469	$86.65	$86.65	$86.60
Purchase #3	$125.54	6.667%	$133.9098	$133.91	$133.90	$133.90
Purchase #4	$104.88	4.346%	$109.4381	$109.44	$109.45	$109.40
Purchase #5	$120.25	6.386%	$127.9292	$127.93	$127.95	$127.90
Purchase #6	$90.89	13.680%	$103.3238	$103.32	$103.30	$103.30
Purchase #7	$144.94	7.159%	$155.3163	$155.32	$155.30	$155.30
7 purchase totals =	$836.03		$902.0784	$902.08	$902.05	$901.90