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	$60.51	4.294%	$63.1083	$63.11	$63.10	$63.10
Purchase #2	$58.29	4.527%	$60.9288	$60.93	$60.95	$60.90
Purchase #3	$125.41	9.541%	$137.3754	$137.38	$137.40	$137.40
Purchase #4	$42.49	4.644%	$44.4632	$44.46	$44.45	$44.50
Purchase #5	$18.59	10.606%	$20.5617	$20.56	$20.55	$20.60
Purchase #6	$56.94	10.321%	$62.8168	$62.82	$62.80	$62.80
Purchase #7	$162.56	11.438%	$181.1536	$181.15	$181.15	$181.20
7 purchase totals =	$524.79		$570.4078	$570.41	$570.40	$570.50