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	$125.31	7.859%	$135.1581	$135.16	$135.15	$135.20
Purchase #2	$165.25	3.611%	$171.2172	$171.22	$171.20	$171.20
Purchase #3	$11.89	3.871%	$12.3503	$12.35	$12.35	$12.40
Purchase #4	$139.57	3.145%	$143.9595	$143.96	$143.95	$144.00
Purchase #5	$105.97	4.822%	$111.0799	$111.08	$111.10	$111.10
Purchase #6	$146.27	13.427%	$165.9097	$165.91	$165.90	$165.90
Purchase #7	$19.63	4.208%	$20.456	$20.46	$20.45	$20.50
7 purchase totals =	$713.89		$760.1307	$760.14	$760.10	$760.30