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	$67.95	7.130%	$72.7948	$72.79	$72.80	$72.80
Purchase #2	$139.34	3.237%	$143.8504	$143.85	$143.85	$143.90
Purchase #3	$133.45	3.516%	$138.1421	$138.14	$138.15	$138.10
Purchase #4	$88.31	3.861%	$91.7196	$91.72	$91.70	$91.70
Purchase #5	$155.81	10.585%	$172.3025	$172.30	$172.30	$172.30
Purchase #6	$14.84	8.465%	$16.0962	$16.10	$16.10	$16.10
Purchase #7	$143.86	5.355%	$151.5637	$151.56	$151.55	$151.60
7 purchase totals =	$743.56		$786.4693	$786.46	$786.45	$786.50