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	$44.83	7.849%	$48.3487	$48.35	$48.35	$48.30
Purchase #2	$192.28	13.623%	$218.4743	$218.47	$218.45	$218.50
Purchase #3	$16.50	10.808%	$18.2833	$18.28	$18.30	$18.30
Purchase #4	$55.67	10.134%	$61.3116	$61.31	$61.30	$61.30
Purchase #5	$12.28	13.865%	$13.9826	$13.98	$14.00	$14.00
Purchase #6	$54.60	13.822%	$62.1468	$62.15	$62.15	$62.10
Purchase #7	$85.39	4.572%	$89.294	$89.29	$89.30	$89.30
7 purchase totals =	$461.55		$511.8413	$511.83	$511.85	$511.80