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	$83.55	11.118%	$92.8391	$92.84	$92.85	$92.80
Purchase #2	$151.72	13.761%	$172.5982	$172.60	$172.60	$172.60
Purchase #3	$96.98	5.363%	$102.181	$102.18	$102.20	$102.20
Purchase #4	$64.26	10.874%	$71.2476	$71.25	$71.25	$71.20
Purchase #5	$172.34	6.828%	$184.1074	$184.11	$184.10	$184.10
Purchase #6	$176.90	13.369%	$200.5498	$200.55	$200.55	$200.50
Purchase #7	$88.82	11.701%	$99.2128	$99.21	$99.20	$99.20
7 purchase totals =	$834.57		$922.7359	$922.74	$922.75	$922.60