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	$95.31	4.519%	$99.6171	$99.62	$99.60	$99.60
Purchase #2	$60.62	4.354%	$63.2594	$63.26	$63.25	$63.30
Purchase #3	$243.39	13.358%	$275.902	$275.90	$275.90	$275.90
Purchase #4	$30.26	7.488%	$32.5259	$32.53	$32.55	$32.50
Purchase #5	$75.51	12.686%	$85.0892	$85.09	$85.10	$85.10
Purchase #6	$50.94	12.138%	$57.1231	$57.12	$57.10	$57.10
Purchase #7	$150.53	3.732%	$156.1478	$156.15	$156.15	$156.10
7 purchase totals =	$706.56		$769.6645	$769.67	$769.65	$769.60