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	$57.42	3.414%	$59.3803	$59.38	$59.40	$59.40
Purchase #2	$136.69	12.583%	$153.8897	$153.89	$153.90	$153.90
Purchase #3	$134.78	11.144%	$149.7999	$149.80	$149.80	$149.80
Purchase #4	$107.63	5.316%	$113.3516	$113.35	$113.35	$113.40
Purchase #5	$157.30	5.410%	$165.8099	$165.81	$165.80	$165.80
Purchase #6	$11.46	12.722%	$12.9179	$12.92	$12.90	$12.90
Purchase #7	$119.96	5.407%	$126.4462	$126.45	$126.45	$126.40
7 purchase totals =	$725.24		$781.5955	$781.60	$781.60	$781.60