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	$172.45	7.401%	$185.213	$185.21	$185.20	$185.20
Purchase #2	$65.30	12.848%	$73.6897	$73.69	$73.70	$73.70
Purchase #3	$239.32	8.258%	$259.083	$259.08	$259.10	$259.10
Purchase #4	$229.33	12.583%	$258.1866	$258.19	$258.20	$258.20
Purchase #5	$39.33	10.300%	$43.381	$43.38	$43.40	$43.40
Purchase #6	$242.92	11.338%	$270.4623	$270.46	$270.45	$270.50
Purchase #7	$55.25	4.784%	$57.8932	$57.89	$57.90	$57.90
7 purchase totals =	$1,043.90		$1,147.9088	$1,147.90	$1,147.95	$1,148.00