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	$60.96	4.794%	$63.8824	$63.88	$63.90	$63.90
Purchase #2	$97.68	7.663%	$105.1652	$105.17	$105.15	$105.20
Purchase #3	$34.93	12.742%	$39.3808	$39.38	$39.40	$39.40
Purchase #4	$160.82	6.344%	$171.0224	$171.02	$171.00	$171.00
Purchase #5	$100.67	13.373%	$114.1326	$114.13	$114.15	$114.10
Purchase #6	$69.55	13.453%	$78.9066	$78.91	$78.90	$78.90
Purchase #7	$231.49	7.154%	$248.0508	$248.05	$248.05	$248.10
7 purchase totals =	$756.10		$820.5408	$820.54	$820.55	$820.60