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	$131.53	5.398%	$138.63	$138.63	$138.65	$138.60
Purchase #2	$92.46	7.442%	$99.3409	$99.34	$99.35	$99.30
Purchase #3	$169.72	4.233%	$176.9042	$176.90	$176.90	$176.90
Purchase #4	$120.59	13.721%	$137.1362	$137.14	$137.15	$137.10
Purchase #5	$22.52	8.320%	$24.3937	$24.39	$24.40	$24.40
Purchase #6	$124.91	4.525%	$130.5622	$130.56	$130.55	$130.60
Purchase #7	$63.50	6.234%	$67.4586	$67.46	$67.45	$67.50
7 purchase totals =	$725.23		$774.4258	$774.42	$774.45	$774.40