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	$91.94	8.469%	$99.7264	$99.73	$99.75	$99.70
Purchase #2	$73.47	10.147%	$80.925	$80.93	$80.95	$80.90
Purchase #3	$187.56	4.697%	$196.3697	$196.37	$196.35	$196.40
Purchase #4	$102.76	12.126%	$115.2207	$115.22	$115.20	$115.20
Purchase #5	$37.85	3.365%	$39.1237	$39.12	$39.10	$39.10
Purchase #6	$191.96	5.784%	$203.063	$203.06	$203.05	$203.10
Purchase #7	$75.62	10.325%	$83.4278	$83.43	$83.45	$83.40
7 purchase totals =	$761.16		$817.8563	$817.86	$817.85	$817.80