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	$97.81	11.275%	$108.8381	$108.84	$108.85	$108.80
Purchase #2	$196.86	9.644%	$215.8452	$215.85	$215.85	$215.80
Purchase #3	$56.42	9.697%	$61.891	$61.89	$61.90	$61.90
Purchase #4	$66.53	8.380%	$72.1052	$72.11	$72.10	$72.10
Purchase #5	$58.32	6.608%	$62.1738	$62.17	$62.15	$62.20
Purchase #6	$220.46	10.610%	$243.8508	$243.85	$243.85	$243.90
Purchase #7	$107.73	8.748%	$117.1542	$117.15	$117.15	$117.20
7 purchase totals =	$804.13		$881.8583	$881.86	$881.85	$881.90