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	$32.36	9.444%	$35.4161	$35.42	$35.40	$35.40
Purchase #2	$114.66	11.290%	$127.6051	$127.61	$127.60	$127.60
Purchase #3	$216.58	9.622%	$237.4193	$237.42	$237.40	$237.40
Purchase #4	$246.98	8.777%	$268.6574	$268.66	$268.65	$268.70
Purchase #5	$250.93	8.766%	$272.9265	$272.93	$272.95	$272.90
Purchase #6	$76.47	7.283%	$82.0393	$82.04	$82.05	$82.00
Purchase #7	$134.84	7.166%	$144.5026	$144.50	$144.50	$144.50
7 purchase totals =	$1,072.82		$1,168.5663	$1,168.58	$1,168.55	$1,168.50