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	$117.37	3.132%	$121.046	$121.05	$121.05	$121.00
Purchase #2	$52.96	8.430%	$57.4245	$57.42	$57.40	$57.40
Purchase #3	$126.88	12.159%	$142.3073	$142.31	$142.30	$142.30
Purchase #4	$37.66	10.787%	$41.7224	$41.72	$41.70	$41.70
Purchase #5	$61.78	7.185%	$66.2189	$66.22	$66.20	$66.20
Purchase #6	$99.60	4.833%	$104.4137	$104.41	$104.40	$104.40
Purchase #7	$196.34	11.268%	$218.4636	$218.46	$218.45	$218.50
7 purchase totals =	$692.59		$751.5964	$751.59	$751.50	$751.50