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	$172.67	10.789%	$191.2994	$191.30	$191.30	$191.30
Purchase #2	$157.71	6.421%	$167.8366	$167.84	$167.85	$167.80
Purchase #3	$201.70	5.741%	$213.2796	$213.28	$213.30	$213.30
Purchase #4	$87.51	4.503%	$91.4506	$91.45	$91.45	$91.50
Purchase #5	$128.76	12.177%	$144.4391	$144.44	$144.45	$144.40
Purchase #6	$136.98	10.814%	$151.793	$151.79	$151.80	$151.80
Purchase #7	$208.80	13.428%	$236.8377	$236.84	$236.85	$236.80
7 purchase totals =	$1,094.13		$1,196.9360	$1,196.94	$1,197.00	$1,196.90