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	$208.81	9.829%	$229.3339	$229.33	$229.35	$229.30
Purchase #2	$222.57	9.825%	$244.4375	$244.44	$244.45	$244.40
Purchase #3	$39.97	8.616%	$43.4138	$43.41	$43.40	$43.40
Purchase #4	$199.86	8.316%	$216.4804	$216.48	$216.50	$216.50
Purchase #5	$127.92	3.835%	$132.8257	$132.83	$132.85	$132.80
Purchase #6	$217.70	7.297%	$233.5856	$233.59	$233.60	$233.60
Purchase #7	$36.82	9.596%	$40.3532	$40.35	$40.35	$40.40
7 purchase totals =	$1,053.65		$1,140.4301	$1,140.43	$1,140.50	$1,140.40