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	$147.71	8.446%	$160.1856	$160.19	$160.20	$160.20
Purchase #2	$97.99	8.704%	$106.519	$106.52	$106.50	$106.50
Purchase #3	$119.26	10.302%	$131.5462	$131.55	$131.55	$131.50
Purchase #4	$138.50	4.532%	$144.7768	$144.78	$144.80	$144.80
Purchase #5	$72.53	13.160%	$82.0749	$82.07	$82.05	$82.10
Purchase #6	$153.84	11.734%	$171.8916	$171.89	$171.90	$171.90
Purchase #7	$99.44	13.175%	$112.5412	$112.54	$112.55	$112.50
7 purchase totals =	$829.27		$909.5353	$909.54	$909.55	$909.50