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	$84.79	7.221%	$90.9127	$90.91	$90.90	$90.90
Purchase #2	$102.98	8.716%	$111.9557	$111.96	$111.95	$112.00
Purchase #3	$179.85	6.328%	$191.2309	$191.23	$191.25	$191.20
Purchase #4	$185.93	3.197%	$191.8742	$191.87	$191.85	$191.90
Purchase #5	$65.33	10.594%	$72.2511	$72.25	$72.25	$72.30
Purchase #6	$144.76	7.854%	$156.1295	$156.13	$156.15	$156.10
Purchase #7	$190.36	13.508%	$216.0738	$216.07	$216.05	$216.10
7 purchase totals =	$954.00		$1,030.4279	$1,030.42	$1,030.40	$1,030.50