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	$122.29	3.716%	$126.8343	$126.83	$126.85	$126.80
Purchase #2	$240.33	4.419%	$250.9502	$250.95	$250.95	$251.00
Purchase #3	$170.67	13.187%	$193.1763	$193.18	$193.20	$193.20
Purchase #4	$111.32	3.639%	$115.3709	$115.37	$115.35	$115.40
Purchase #5	$105.48	5.807%	$111.6052	$111.61	$111.60	$111.60
Purchase #6	$82.59	3.277%	$85.2965	$85.30	$85.30	$85.30
Purchase #7	$125.83	8.802%	$136.9056	$136.91	$136.90	$136.90
7 purchase totals =	$958.51		$1,020.1390	$1,020.15	$1,020.15	$1,020.20