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	$53.53	11.190%	$59.52	$59.52	$59.50	$59.50
Purchase #2	$247.44	7.279%	$265.4512	$265.45	$265.45	$265.50
Purchase #3	$67.67	12.334%	$76.0164	$76.02	$76.00	$76.00
Purchase #4	$125.54	3.582%	$130.0368	$130.04	$130.05	$130.00
Purchase #5	$71.66	13.841%	$81.5785	$81.58	$81.60	$81.60
Purchase #6	$44.37	13.704%	$50.4505	$50.45	$50.45	$50.50
Purchase #7	$122.27	7.578%	$131.5356	$131.54	$131.55	$131.50
7 purchase totals =	$732.48		$794.5890	$794.60	$794.60	$794.60