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	$152.75	10.716%	$169.1187	$169.12	$169.10	$169.10
Purchase #2	$26.63	9.167%	$29.0712	$29.07	$29.05	$29.10
Purchase #3	$146.98	12.655%	$165.5803	$165.58	$165.60	$165.60
Purchase #4	$83.86	8.574%	$91.0502	$91.05	$91.05	$91.10
Purchase #5	$176.85	11.158%	$196.5829	$196.58	$196.60	$196.60
Purchase #6	$173.50	9.695%	$190.3208	$190.32	$190.30	$190.30
Purchase #7	$28.85	4.449%	$30.1335	$30.13	$30.15	$30.10
7 purchase totals =	$789.42		$871.8576	$871.85	$871.85	$871.90