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	$96.35	8.735%	$104.7662	$104.77	$104.75	$104.80
Purchase #2	$113.73	11.858%	$127.2161	$127.22	$127.20	$127.20
Purchase #3	$62.37	12.438%	$70.1276	$70.13	$70.15	$70.10
Purchase #4	$28.81	10.560%	$31.8523	$31.85	$31.85	$31.90
Purchase #5	$71.42	10.515%	$78.9298	$78.93	$78.95	$78.90
Purchase #6	$176.37	13.679%	$200.4957	$200.50	$200.50	$200.50
Purchase #7	$204.62	3.420%	$211.618	$211.62	$211.60	$211.60
7 purchase totals =	$753.67		$825.0057	$825.02	$825.00	$825.00