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	$169.49	9.681%	$185.8983	$185.90	$185.90	$185.90
Purchase #2	$87.89	10.244%	$96.8935	$96.89	$96.90	$96.90
Purchase #3	$198.73	6.553%	$211.7528	$211.75	$211.75	$211.80
Purchase #4	$166.72	12.525%	$187.6017	$187.60	$187.60	$187.60
Purchase #5	$26.63	7.203%	$28.5482	$28.55	$28.55	$28.50
Purchase #6	$150.39	3.164%	$155.1483	$155.15	$155.15	$155.10
Purchase #7	$231.53	10.159%	$255.0511	$255.05	$255.05	$255.10
7 purchase totals =	$1,031.38		$1,120.8939	$1,120.89	$1,120.90	$1,120.90