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	$78.64	4.300%	$82.0215	$82.02	$82.00	$82.00
Purchase #2	$109.47	13.515%	$124.2649	$124.26	$124.25	$124.30
Purchase #3	$197.77	13.658%	$224.7814	$224.78	$224.80	$224.80
Purchase #4	$32.31	6.352%	$34.3623	$34.36	$34.35	$34.40
Purchase #5	$157.90	9.377%	$172.7063	$172.71	$172.70	$172.70
Purchase #6	$159.66	8.241%	$172.8176	$172.82	$172.80	$172.80
Purchase #7	$237.58	8.115%	$256.8596	$256.86	$256.85	$256.90
7 purchase totals =	$973.33		$1,067.8136	$1,067.81	$1,067.75	$1,067.90