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	$35.66	4.440%	$37.2433	$37.24	$37.25	$37.20
Purchase #2	$98.68	6.466%	$105.0606	$105.06	$105.05	$105.10
Purchase #3	$245.29	8.388%	$265.8649	$265.86	$265.85	$265.90
Purchase #4	$20.72	6.234%	$22.0117	$22.01	$22.00	$22.00
Purchase #5	$43.31	12.695%	$48.8082	$48.81	$48.80	$48.80
Purchase #6	$208.90	6.145%	$221.7369	$221.74	$221.75	$221.70
Purchase #7	$159.77	7.849%	$172.3103	$172.31	$172.30	$172.30
7 purchase totals =	$812.33		$873.0359	$873.03	$873.00	$873.00