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	$54.55	8.676%	$59.2828	$59.28	$59.30	$59.30
Purchase #2	$144.49	4.391%	$150.8346	$150.83	$150.85	$150.80
Purchase #3	$150.28	9.267%	$164.2064	$164.21	$164.20	$164.20
Purchase #4	$87.61	12.257%	$98.3484	$98.35	$98.35	$98.30
Purchase #5	$27.62	4.665%	$28.9085	$28.91	$28.90	$28.90
Purchase #6	$130.91	13.336%	$148.3682	$148.37	$148.35	$148.40
Purchase #7	$69.51	12.361%	$78.1021	$78.10	$78.10	$78.10
7 purchase totals =	$664.97		$728.0510	$728.05	$728.05	$728.00