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	$87.69	4.680%	$91.7939	$91.79	$91.80	$91.80
Purchase #2	$51.82	7.113%	$55.506	$55.51	$55.50	$55.50
Purchase #3	$86.54	6.142%	$91.8553	$91.86	$91.85	$91.90
Purchase #4	$123.63	7.469%	$132.8639	$132.86	$132.85	$132.90
Purchase #5	$225.73	9.328%	$246.7861	$246.79	$246.80	$246.80
Purchase #6	$149.69	8.547%	$162.484	$162.48	$162.50	$162.50
Purchase #7	$127.36	13.123%	$144.0735	$144.07	$144.05	$144.10
7 purchase totals =	$852.46		$925.3627	$925.36	$925.35	$925.50