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	$33.33	7.695%	$35.8947	$35.89	$35.90	$35.90
Purchase #2	$29.33	5.397%	$30.9129	$30.91	$30.90	$30.90
Purchase #3	$162.91	6.643%	$173.7321	$173.73	$173.75	$173.70
Purchase #4	$250.43	9.611%	$274.4988	$274.50	$274.50	$274.50
Purchase #5	$158.40	5.517%	$167.1389	$167.14	$167.15	$167.10
Purchase #6	$246.78	3.825%	$256.2193	$256.22	$256.20	$256.20
Purchase #7	$130.61	9.674%	$143.2452	$143.25	$143.25	$143.20
7 purchase totals =	$1,011.79		$1,081.6419	$1,081.64	$1,081.65	$1,081.50