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	$182.81	9.441%	$200.0691	$200.07	$200.05	$200.10
Purchase #2	$180.32	3.420%	$186.4869	$186.49	$186.50	$186.50
Purchase #3	$7.78	9.754%	$8.5389	$8.54	$8.55	$8.50
Purchase #4	$78.68	6.529%	$83.817	$83.82	$83.80	$83.80
Purchase #5	$154.60	12.479%	$173.8925	$173.89	$173.90	$173.90
Purchase #6	$217.72	11.830%	$243.4763	$243.48	$243.50	$243.50
Purchase #7	$143.33	11.358%	$159.6094	$159.61	$159.60	$159.60
7 purchase totals =	$965.24		$1,055.8901	$1,055.90	$1,055.90	$1,055.90