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	$88.27	12.373%	$99.1916	$99.19	$99.20	$99.20
Purchase #2	$238.68	11.127%	$265.2379	$265.24	$265.25	$265.20
Purchase #3	$131.60	6.128%	$139.6644	$139.66	$139.65	$139.70
Purchase #4	$175.79	5.282%	$185.0752	$185.08	$185.10	$185.10
Purchase #5	$53.62	13.551%	$60.886	$60.89	$60.90	$60.90
Purchase #6	$75.43	4.281%	$78.6592	$78.66	$78.65	$78.70
Purchase #7	$218.75	7.117%	$234.3184	$234.32	$234.30	$234.30
7 purchase totals =	$982.14		$1,063.0327	$1,063.04	$1,063.05	$1,063.10