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	$179.63	13.284%	$203.492	$203.49	$203.50	$203.50
Purchase #2	$29.66	13.367%	$33.6247	$33.62	$33.60	$33.60
Purchase #3	$105.64	13.120%	$119.5	$119.50	$119.50	$119.50
Purchase #4	$37.90	6.287%	$40.2828	$40.28	$40.30	$40.30
Purchase #5	$92.77	8.622%	$100.7686	$100.77	$100.75	$100.80
Purchase #6	$70.27	8.338%	$76.1291	$76.13	$76.15	$76.10
Purchase #7	$166.83	5.194%	$175.4952	$175.50	$175.50	$175.50
7 purchase totals =	$682.70		$749.2924	$749.29	$749.30	$749.30