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	$20.73	5.302%	$21.8291	$21.83	$21.85	$21.80
Purchase #2	$76.28	8.870%	$83.046	$83.05	$83.05	$83.00
Purchase #3	$215.42	11.107%	$239.3467	$239.35	$239.35	$239.30
Purchase #4	$134.86	3.372%	$139.4075	$139.41	$139.40	$139.40
Purchase #5	$149.57	5.251%	$157.4239	$157.42	$157.40	$157.40
Purchase #6	$129.53	10.852%	$143.5866	$143.59	$143.60	$143.60
Purchase #7	$250.83	10.490%	$277.1421	$277.14	$277.15	$277.10
7 purchase totals =	$977.22		$1,061.7819	$1,061.79	$1,061.80	$1,061.60