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	$120.93	8.849%	$131.6311	$131.63	$131.65	$131.60
Purchase #2	$48.45	7.345%	$52.0087	$52.01	$52.00	$52.00
Purchase #3	$94.86	13.383%	$107.5551	$107.56	$107.55	$107.60
Purchase #4	$90.86	12.434%	$102.1575	$102.16	$102.15	$102.20
Purchase #5	$92.52	13.668%	$105.1656	$105.17	$105.15	$105.20
Purchase #6	$30.46	11.499%	$33.9626	$33.96	$33.95	$34.00
Purchase #7	$45.46	6.743%	$48.5254	$48.53	$48.55	$48.50
7 purchase totals =	$523.54		$581.0060	$581.02	$581.00	$581.10