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	$85.65	8.693%	$93.0956	$93.10	$93.10	$93.10
Purchase #2	$75.83	12.495%	$85.305	$85.31	$85.30	$85.30
Purchase #3	$87.33	5.241%	$91.907	$91.91	$91.90	$91.90
Purchase #4	$12.72	5.194%	$13.3807	$13.38	$13.40	$13.40
Purchase #5	$11.52	5.413%	$12.1436	$12.14	$12.15	$12.10
Purchase #6	$227.96	4.769%	$238.8314	$238.83	$238.85	$238.80
Purchase #7	$245.83	5.198%	$258.6082	$258.61	$258.60	$258.60
7 purchase totals =	$746.84		$793.2715	$793.28	$793.30	$793.20