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	$86.94	3.175%	$89.7003	$89.70	$89.70	$89.70
Purchase #2	$175.62	5.177%	$184.7118	$184.71	$184.70	$184.70
Purchase #3	$54.96	11.678%	$61.3782	$61.38	$61.40	$61.40
Purchase #4	$161.37	12.471%	$181.4945	$181.49	$181.50	$181.50
Purchase #5	$193.39	12.194%	$216.972	$216.97	$216.95	$217.00
Purchase #6	$187.62	4.630%	$196.3068	$196.31	$196.30	$196.30
Purchase #7	$125.47	11.709%	$140.1613	$140.16	$140.15	$140.20
7 purchase totals =	$985.37		$1,070.7249	$1,070.72	$1,070.70	$1,070.80