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	$234.98	13.117%	$265.8023	$265.80	$265.80	$265.80
Purchase #2	$86.89	3.330%	$89.7834	$89.78	$89.80	$89.80
Purchase #3	$25.77	7.166%	$27.6167	$27.62	$27.60	$27.60
Purchase #4	$166.33	13.441%	$188.6864	$188.69	$188.70	$188.70
Purchase #5	$33.87	5.430%	$35.7091	$35.71	$35.70	$35.70
Purchase #6	$182.77	9.425%	$199.9961	$200.00	$200.00	$200.00
Purchase #7	$157.76	4.388%	$164.6825	$164.68	$164.70	$164.70
7 purchase totals =	$888.37		$972.2765	$972.28	$972.30	$972.30