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	$137.47	10.636%	$152.0913	$152.09	$152.10	$152.10
Purchase #2	$160.87	5.342%	$169.4637	$169.46	$169.45	$169.50
Purchase #3	$232.97	11.139%	$258.9205	$258.92	$258.90	$258.90
Purchase #4	$179.82	9.379%	$196.6853	$196.69	$196.70	$196.70
Purchase #5	$102.62	8.199%	$111.0338	$111.03	$111.05	$111.00
Purchase #6	$214.80	12.364%	$241.3579	$241.36	$241.35	$241.40
Purchase #7	$67.91	9.821%	$74.5794	$74.58	$74.60	$74.60
7 purchase totals =	$1,096.46		$1,204.1319	$1,204.13	$1,204.15	$1,204.20