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	$120.59	8.675%	$131.0512	$131.05	$131.05	$131.10
Purchase #2	$185.28	5.874%	$196.1633	$196.16	$196.15	$196.20
Purchase #3	$243.25	7.825%	$262.2843	$262.28	$262.30	$262.30
Purchase #4	$40.90	3.840%	$42.4706	$42.47	$42.45	$42.50
Purchase #5	$117.65	11.155%	$130.7739	$130.77	$130.75	$130.80
Purchase #6	$77.73	12.356%	$87.3343	$87.33	$87.35	$87.30
Purchase #7	$199.92	7.580%	$215.0739	$215.07	$215.05	$215.10
7 purchase totals =	$985.32		$1,065.1515	$1,065.13	$1,065.10	$1,065.30