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	$206.38	3.562%	$213.7313	$213.73	$213.75	$213.70
Purchase #2	$100.47	7.266%	$107.7702	$107.77	$107.75	$107.80
Purchase #3	$137.40	13.582%	$156.0617	$156.06	$156.05	$156.10
Purchase #4	$60.38	11.267%	$67.183	$67.18	$67.20	$67.20
Purchase #5	$231.55	10.485%	$255.828	$255.83	$255.85	$255.80
Purchase #6	$235.91	9.863%	$259.1778	$259.18	$259.20	$259.20
Purchase #7	$113.32	12.435%	$127.4113	$127.41	$127.40	$127.40
7 purchase totals =	$1,085.41		$1,187.1633	$1,187.16	$1,187.20	$1,187.20