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	$76.90	11.462%	$85.7143	$85.71	$85.70	$85.70
Purchase #2	$83.94	7.774%	$90.4655	$90.47	$90.45	$90.50
Purchase #3	$159.61	4.156%	$166.2434	$166.24	$166.25	$166.20
Purchase #4	$79.45	8.796%	$86.4384	$86.44	$86.45	$86.40
Purchase #5	$93.91	3.124%	$96.8437	$96.84	$96.85	$96.80
Purchase #6	$200.75	13.577%	$228.0058	$228.01	$228.00	$228.00
Purchase #7	$84.89	11.121%	$94.3306	$94.33	$94.35	$94.30
7 purchase totals =	$779.45		$848.0417	$848.04	$848.05	$847.90