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	$174.30	8.196%	$188.5856	$188.59	$188.60	$188.60
Purchase #2	$35.29	3.526%	$36.5343	$36.53	$36.55	$36.50
Purchase #3	$169.89	12.787%	$191.6138	$191.61	$191.60	$191.60
Purchase #4	$99.41	13.373%	$112.7041	$112.70	$112.70	$112.70
Purchase #5	$248.84	6.699%	$265.5098	$265.51	$265.50	$265.50
Purchase #6	$137.50	3.155%	$141.8381	$141.84	$141.85	$141.80
Purchase #7	$117.71	5.384%	$124.0475	$124.05	$124.05	$124.00
7 purchase totals =	$982.94		$1,060.8332	$1,060.83	$1,060.85	$1,060.70