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	$26.84	6.182%	$28.4992	$28.50	$28.50	$28.50
Purchase #2	$117.42	8.468%	$127.3631	$127.36	$127.35	$127.40
Purchase #3	$88.66	12.674%	$99.8968	$99.90	$99.90	$99.90
Purchase #4	$191.41	5.825%	$202.5596	$202.56	$202.55	$202.60
Purchase #5	$216.66	7.475%	$232.8553	$232.86	$232.85	$232.90
Purchase #6	$248.98	12.496%	$280.0925	$280.09	$280.10	$280.10
Purchase #7	$89.79	11.115%	$99.7702	$99.77	$99.75	$99.80
7 purchase totals =	$979.76		$1,071.0367	$1,071.04	$1,071.00	$1,071.20