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	$91.78	10.434%	$101.3563	$101.36	$101.35	$101.40
Purchase #2	$241.60	4.765%	$253.1122	$253.11	$253.10	$253.10
Purchase #3	$162.48	6.137%	$172.4514	$172.45	$172.45	$172.50
Purchase #4	$84.35	6.199%	$89.5789	$89.58	$89.60	$89.60
Purchase #5	$94.73	8.315%	$102.6068	$102.61	$102.60	$102.60
Purchase #6	$228.55	10.388%	$252.2918	$252.29	$252.30	$252.30
Purchase #7	$78.85	13.250%	$89.2976	$89.30	$89.30	$89.30
7 purchase totals =	$982.34		$1,060.6950	$1,060.70	$1,060.70	$1,060.80