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	$239.78	6.205%	$254.6583	$254.66	$254.65	$254.70
Purchase #2	$85.61	4.131%	$89.1465	$89.15	$89.15	$89.10
Purchase #3	$157.35	6.741%	$167.957	$167.96	$167.95	$168.00
Purchase #4	$86.37	9.160%	$94.2815	$94.28	$94.30	$94.30
Purchase #5	$137.33	11.167%	$152.6656	$152.67	$152.65	$152.70
Purchase #6	$14.60	5.662%	$15.4267	$15.43	$15.45	$15.40
Purchase #7	$91.82	5.776%	$97.1235	$97.12	$97.10	$97.10
7 purchase totals =	$812.86		$871.2591	$871.27	$871.25	$871.30