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	$93.93	8.119%	$101.5562	$101.56	$101.55	$101.60
Purchase #2	$57.82	7.422%	$62.1114	$62.11	$62.10	$62.10
Purchase #3	$200.49	13.192%	$226.9386	$226.94	$226.95	$226.90
Purchase #4	$63.41	6.799%	$67.7212	$67.72	$67.70	$67.70
Purchase #5	$98.53	13.702%	$112.0306	$112.03	$112.05	$112.00
Purchase #6	$95.66	5.164%	$100.5999	$100.60	$100.60	$100.60
Purchase #7	$130.34	5.392%	$137.3679	$137.37	$137.35	$137.40
7 purchase totals =	$740.18		$808.3258	$808.33	$808.30	$808.30