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	$82.46	10.853%	$91.4094	$91.41	$91.40	$91.40
Purchase #2	$25.76	7.702%	$27.744	$27.74	$27.75	$27.70
Purchase #3	$163.69	5.163%	$172.1413	$172.14	$172.15	$172.10
Purchase #4	$139.28	4.442%	$145.4668	$145.47	$145.45	$145.50
Purchase #5	$122.81	7.424%	$131.9274	$131.93	$131.95	$131.90
Purchase #6	$143.88	9.480%	$157.5198	$157.52	$157.50	$157.50
Purchase #7	$33.71	12.771%	$38.0151	$38.02	$38.00	$38.00
7 purchase totals =	$711.59		$764.2238	$764.23	$764.20	$764.10