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	$77.59	10.328%	$85.6035	$85.60	$85.60	$85.60
Purchase #2	$88.93	12.228%	$99.8044	$99.80	$99.80	$99.80
Purchase #3	$140.85	3.533%	$145.8262	$145.83	$145.85	$145.80
Purchase #4	$35.32	12.637%	$39.7834	$39.78	$39.80	$39.80
Purchase #5	$21.71	6.746%	$23.1746	$23.17	$23.15	$23.20
Purchase #6	$187.74	10.406%	$207.2762	$207.28	$207.30	$207.30
Purchase #7	$148.56	11.126%	$165.0888	$165.09	$165.10	$165.10
7 purchase totals =	$700.70		$766.5571	$766.55	$766.60	$766.60