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	$11.86	4.260%	$12.3652	$12.37	$12.35	$12.40
Purchase #2	$191.29	10.465%	$211.3085	$211.31	$211.30	$211.30
Purchase #3	$123.70	3.697%	$128.2732	$128.27	$128.25	$128.30
Purchase #4	$12.40	9.106%	$13.5291	$13.53	$13.55	$13.50
Purchase #5	$49.43	10.802%	$54.7694	$54.77	$54.75	$54.80
Purchase #6	$170.71	11.462%	$190.2768	$190.28	$190.30	$190.30
Purchase #7	$131.87	5.393%	$138.9817	$138.98	$139.00	$139.00
7 purchase totals =	$691.26		$749.5039	$749.51	$749.50	$749.60