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	$83.73	3.684%	$86.8146	$86.81	$86.80	$86.80
Purchase #2	$245.76	13.561%	$279.0875	$279.09	$279.10	$279.10
Purchase #3	$6.31	11.543%	$7.0384	$7.04	$7.05	$7.00
Purchase #4	$25.79	10.536%	$28.5072	$28.51	$28.50	$28.50
Purchase #5	$72.95	5.430%	$76.9112	$76.91	$76.90	$76.90
Purchase #6	$145.35	3.204%	$150.007	$150.01	$150.00	$150.00
Purchase #7	$35.26	11.580%	$39.3431	$39.34	$39.35	$39.30
7 purchase totals =	$615.15		$667.7090	$667.71	$667.70	$667.60