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	$136.56	10.373%	$150.7254	$150.73	$150.75	$150.70
Purchase #2	$171.91	6.252%	$182.6578	$182.66	$182.65	$182.70
Purchase #3	$57.82	11.413%	$64.419	$64.42	$64.40	$64.40
Purchase #4	$24.89	10.459%	$27.4932	$27.49	$27.50	$27.50
Purchase #5	$236.82	9.573%	$259.4908	$259.49	$259.50	$259.50
Purchase #6	$85.56	3.125%	$88.2338	$88.23	$88.25	$88.20
Purchase #7	$226.89	7.839%	$244.6759	$244.68	$244.70	$244.70
7 purchase totals =	$940.45		$1,017.6959	$1,017.70	$1,017.75	$1,017.70