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	$99.83	4.596%	$104.4182	$104.42	$104.40	$104.40
Purchase #2	$62.42	12.539%	$70.2468	$70.25	$70.25	$70.20
Purchase #3	$72.93	13.257%	$82.5983	$82.60	$82.60	$82.60
Purchase #4	$10.71	6.490%	$11.4051	$11.41	$11.40	$11.40
Purchase #5	$37.40	5.457%	$39.4409	$39.44	$39.45	$39.40
Purchase #6	$9.50	9.804%	$10.4314	$10.43	$10.45	$10.40
Purchase #7	$40.25	12.267%	$45.1875	$45.19	$45.20	$45.20
7 purchase totals =	$333.04		$363.7282	$363.74	$363.75	$363.60