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	$72.54	13.420%	$82.2749	$82.27	$82.25	$82.30
Purchase #2	$208.29	11.833%	$232.937	$232.94	$232.95	$232.90
Purchase #3	$11.54	7.744%	$12.4337	$12.43	$12.45	$12.40
Purchase #4	$30.91	7.578%	$33.2524	$33.25	$33.25	$33.30
Purchase #5	$22.53	4.609%	$23.5684	$23.57	$23.55	$23.60
Purchase #6	$27.51	5.216%	$28.9449	$28.94	$28.95	$28.90
Purchase #7	$31.57	13.496%	$35.8307	$35.83	$35.85	$35.80
7 purchase totals =	$404.89		$449.2420	$449.23	$449.25	$449.20