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	$67.49	6.720%	$72.0253	$72.03	$72.05	$72.00
Purchase #2	$146.65	8.393%	$158.9583	$158.96	$158.95	$159.00
Purchase #3	$41.96	8.448%	$45.5048	$45.50	$45.50	$45.50
Purchase #4	$88.79	13.753%	$101.0013	$101.00	$101.00	$101.00
Purchase #5	$236.70	8.463%	$256.7319	$256.73	$256.75	$256.70
Purchase #6	$119.92	7.154%	$128.4991	$128.50	$128.50	$128.50
Purchase #7	$154.42	4.171%	$160.8609	$160.86	$160.85	$160.90
7 purchase totals =	$855.93		$923.5816	$923.58	$923.60	$923.60