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	$35.28	5.598%	$37.255	$37.26	$37.25	$37.30
Purchase #2	$99.65	5.873%	$105.5024	$105.50	$105.50	$105.50
Purchase #3	$118.88	3.482%	$123.0194	$123.02	$123.00	$123.00
Purchase #4	$156.50	8.372%	$169.6022	$169.60	$169.60	$169.60
Purchase #5	$111.94	12.789%	$126.256	$126.26	$126.25	$126.30
Purchase #6	$37.62	11.680%	$42.014	$42.01	$42.00	$42.00
Purchase #7	$202.90	13.490%	$230.2712	$230.27	$230.25	$230.30
7 purchase totals =	$762.77		$833.9202	$833.92	$833.85	$834.00