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	$236.46	11.803%	$264.3694	$264.37	$264.35	$264.40
Purchase #2	$78.85	5.697%	$83.3421	$83.34	$83.35	$83.30
Purchase #3	$190.44	4.857%	$199.6897	$199.69	$199.70	$199.70
Purchase #4	$167.62	10.322%	$184.9217	$184.92	$184.90	$184.90
Purchase #5	$158.58	13.684%	$180.2801	$180.28	$180.30	$180.30
Purchase #6	$113.35	4.524%	$118.478	$118.48	$118.50	$118.50
Purchase #7	$124.63	12.442%	$140.1365	$140.14	$140.15	$140.10
7 purchase totals =	$1,069.93		$1,171.2175	$1,171.22	$1,171.25	$1,171.20