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	$35.76	4.526%	$37.3785	$37.38	$37.40	$37.40
Purchase #2	$195.89	5.669%	$206.995	$207.00	$207.00	$207.00
Purchase #3	$173.30	9.735%	$190.1708	$190.17	$190.15	$190.20
Purchase #4	$230.46	6.571%	$245.6035	$245.60	$245.60	$245.60
Purchase #5	$187.42	9.306%	$204.8613	$204.86	$204.85	$204.90
Purchase #6	$171.43	9.554%	$187.8084	$187.81	$187.80	$187.80
Purchase #7	$91.87	9.388%	$100.4948	$100.49	$100.50	$100.50
7 purchase totals =	$1,086.13		$1,173.3123	$1,173.31	$1,173.30	$1,173.40