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	$231.50	6.168%	$245.7789	$245.78	$245.80	$245.80
Purchase #2	$7.98	3.752%	$8.2794	$8.28	$8.30	$8.30
Purchase #3	$217.50	3.624%	$225.3822	$225.38	$225.40	$225.40
Purchase #4	$80.67	10.309%	$88.9863	$88.99	$89.00	$89.00
Purchase #5	$125.52	4.158%	$130.7391	$130.74	$130.75	$130.70
Purchase #6	$248.56	12.813%	$280.408	$280.41	$280.40	$280.40
Purchase #7	$34.82	6.748%	$37.1697	$37.17	$37.15	$37.20
7 purchase totals =	$946.55		$1,016.7436	$1,016.75	$1,016.80	$1,016.80