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	$188.65	5.172%	$198.407	$198.41	$198.40	$198.40
Purchase #2	$35.86	5.133%	$37.7007	$37.70	$37.70	$37.70
Purchase #3	$95.55	4.239%	$99.6004	$99.60	$99.60	$99.60
Purchase #4	$112.90	7.213%	$121.0435	$121.04	$121.05	$121.00
Purchase #5	$154.82	11.606%	$172.7884	$172.79	$172.80	$172.80
Purchase #6	$163.34	10.379%	$180.2931	$180.29	$180.30	$180.30
Purchase #7	$47.30	7.524%	$50.8589	$50.86	$50.85	$50.90
7 purchase totals =	$798.42		$860.6920	$860.69	$860.70	$860.70