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	$172.29	13.516%	$195.5767	$195.58	$195.60	$195.60
Purchase #2	$174.98	12.264%	$196.4395	$196.44	$196.45	$196.40
Purchase #3	$200.72	4.256%	$209.2626	$209.26	$209.25	$209.30
Purchase #4	$204.92	6.455%	$218.1476	$218.15	$218.15	$218.10
Purchase #5	$63.82	13.109%	$72.1862	$72.19	$72.20	$72.20
Purchase #6	$56.53	12.409%	$63.5448	$63.54	$63.55	$63.50
Purchase #7	$246.68	13.230%	$279.3158	$279.32	$279.30	$279.30
7 purchase totals =	$1,119.94		$1,234.4732	$1,234.48	$1,234.50	$1,234.40