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	$83.50	13.699%	$94.9387	$94.94	$94.95	$94.90
Purchase #2	$57.71	3.587%	$59.7801	$59.78	$59.80	$59.80
Purchase #3	$139.77	13.642%	$158.8374	$158.84	$158.85	$158.80
Purchase #4	$131.83	3.447%	$136.3742	$136.37	$136.35	$136.40
Purchase #5	$61.48	6.546%	$65.5045	$65.50	$65.50	$65.50
Purchase #6	$224.35	8.674%	$243.8101	$243.81	$243.80	$243.80
Purchase #7	$41.60	13.759%	$47.3237	$47.32	$47.30	$47.30
7 purchase totals =	$740.24		$806.5687	$806.56	$806.55	$806.50