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	$225.28	12.822%	$254.1654	$254.17	$254.15	$254.20
Purchase #2	$119.46	11.333%	$132.9984	$133.00	$133.00	$133.00
Purchase #3	$158.84	8.730%	$172.7067	$172.71	$172.70	$172.70
Purchase #4	$52.27	13.657%	$59.4085	$59.41	$59.40	$59.40
Purchase #5	$49.78	6.804%	$53.167	$53.17	$53.15	$53.20
Purchase #6	$45.89	11.422%	$51.1316	$51.13	$51.15	$51.10
Purchase #7	$35.53	6.288%	$37.7641	$37.76	$37.75	$37.80
7 purchase totals =	$687.05		$761.3417	$761.35	$761.30	$761.40