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	$118.25	5.612%	$124.8862	$124.89	$124.90	$124.90
Purchase #2	$95.95	8.164%	$103.7834	$103.78	$103.80	$103.80
Purchase #3	$150.59	7.811%	$162.3526	$162.35	$162.35	$162.40
Purchase #4	$114.63	3.495%	$118.6363	$118.64	$118.65	$118.60
Purchase #5	$247.79	13.256%	$280.637	$280.64	$280.65	$280.60
Purchase #6	$28.63	5.511%	$30.2078	$30.21	$30.20	$30.20
Purchase #7	$180.43	6.224%	$191.66	$191.66	$191.65	$191.70
7 purchase totals =	$936.27		$1,012.1633	$1,012.17	$1,012.20	$1,012.20