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	$124.95	13.137%	$141.3647	$141.36	$141.35	$141.40
Purchase #2	$24.72	11.165%	$27.48	$27.48	$27.50	$27.50
Purchase #3	$240.31	6.754%	$256.5405	$256.54	$256.55	$256.50
Purchase #4	$159.99	4.623%	$167.3863	$167.39	$167.40	$167.40
Purchase #5	$236.86	13.447%	$268.7106	$268.71	$268.70	$268.70
Purchase #6	$166.61	8.871%	$181.39	$181.39	$181.40	$181.40
Purchase #7	$159.29	8.392%	$172.6576	$172.66	$172.65	$172.70
7 purchase totals =	$1,112.73		$1,215.5297	$1,215.53	$1,215.55	$1,215.60