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	$104.43	7.107%	$111.8518	$111.85	$111.85	$111.90
Purchase #2	$179.53	8.329%	$194.4831	$194.48	$194.50	$194.50
Purchase #3	$83.60	13.457%	$94.8501	$94.85	$94.85	$94.90
Purchase #4	$157.51	4.874%	$165.187	$165.19	$165.20	$165.20
Purchase #5	$149.51	9.848%	$164.2337	$164.23	$164.25	$164.20
Purchase #6	$39.88	4.577%	$41.7053	$41.71	$41.70	$41.70
Purchase #7	$204.72	4.310%	$213.5434	$213.54	$213.55	$213.50
7 purchase totals =	$919.18		$985.8544	$985.85	$985.90	$985.90