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	$72.86	4.496%	$76.1358	$76.14	$76.15	$76.10
Purchase #2	$172.55	12.459%	$194.048	$194.05	$194.05	$194.00
Purchase #3	$113.74	11.568%	$126.8974	$126.90	$126.90	$126.90
Purchase #4	$51.74	7.350%	$55.5429	$55.54	$55.55	$55.50
Purchase #5	$99.57	9.761%	$109.289	$109.29	$109.30	$109.30
Purchase #6	$66.74	8.801%	$72.6138	$72.61	$72.60	$72.60
Purchase #7	$200.96	3.863%	$208.7231	$208.72	$208.70	$208.70
7 purchase totals =	$778.16		$843.2500	$843.25	$843.25	$843.10