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	$168.94	3.532%	$174.907	$174.91	$174.90	$174.90
Purchase #2	$123.49	3.509%	$127.8233	$127.82	$127.80	$127.80
Purchase #3	$200.77	6.612%	$214.0449	$214.04	$214.05	$214.00
Purchase #4	$114.44	13.468%	$129.8528	$129.85	$129.85	$129.90
Purchase #5	$57.82	6.318%	$61.4731	$61.47	$61.45	$61.50
Purchase #6	$191.53	11.571%	$213.6919	$213.69	$213.70	$213.70
Purchase #7	$237.29	5.407%	$250.1203	$250.12	$250.10	$250.10
7 purchase totals =	$1,094.28		$1,171.9133	$1,171.90	$1,171.85	$1,171.90