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	$53.76	5.836%	$56.8974	$56.90	$56.90	$56.90
Purchase #2	$232.72	5.641%	$245.8477	$245.85	$245.85	$245.80
Purchase #3	$103.58	12.452%	$116.4778	$116.48	$116.50	$116.50
Purchase #4	$104.34	11.204%	$116.0303	$116.03	$116.05	$116.00
Purchase #5	$214.30	8.803%	$233.1648	$233.16	$233.15	$233.20
Purchase #6	$211.30	11.864%	$236.3686	$236.37	$236.35	$236.40
Purchase #7	$146.69	4.340%	$153.0563	$153.06	$153.05	$153.10
7 purchase totals =	$1,066.69		$1,157.8429	$1,157.85	$1,157.85	$1,157.90