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	$76.96	6.614%	$82.0501	$82.05	$82.05	$82.10
Purchase #2	$111.92	13.488%	$127.0158	$127.02	$127.00	$127.00
Purchase #3	$63.50	12.654%	$71.5353	$71.54	$71.55	$71.50
Purchase #4	$250.77	4.744%	$262.6665	$262.67	$262.65	$262.70
Purchase #5	$37.99	11.288%	$42.2783	$42.28	$42.30	$42.30
Purchase #6	$217.69	4.367%	$227.1965	$227.20	$227.20	$227.20
Purchase #7	$144.75	13.140%	$163.7702	$163.77	$163.75	$163.80
7 purchase totals =	$903.58		$976.5127	$976.53	$976.50	$976.60