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	$53.27	3.750%	$55.2676	$55.27	$55.25	$55.30
Purchase #2	$244.83	3.535%	$253.4847	$253.48	$253.50	$253.50
Purchase #3	$199.39	8.317%	$215.9733	$215.97	$215.95	$216.00
Purchase #4	$79.84	8.199%	$86.3861	$86.39	$86.40	$86.40
Purchase #5	$121.42	12.747%	$136.8974	$136.90	$136.90	$136.90
Purchase #6	$159.41	9.103%	$173.9211	$173.92	$173.90	$173.90
Purchase #7	$116.51	12.764%	$131.3813	$131.38	$131.40	$131.40
7 purchase totals =	$974.67		$1,053.3115	$1,053.31	$1,053.30	$1,053.40