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	$195.79	10.644%	$216.6299	$216.63	$216.65	$216.60
Purchase #2	$99.54	7.320%	$106.8263	$106.83	$106.85	$106.80
Purchase #3	$35.50	7.203%	$38.0571	$38.06	$38.05	$38.10
Purchase #4	$112.86	6.851%	$120.592	$120.59	$120.60	$120.60
Purchase #5	$105.87	6.312%	$112.5525	$112.55	$112.55	$112.60
Purchase #6	$140.60	8.658%	$152.7731	$152.77	$152.75	$152.80
Purchase #7	$89.32	11.801%	$99.8607	$99.86	$99.85	$99.90
7 purchase totals =	$779.48		$847.2916	$847.29	$847.30	$847.40