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	$102.79	10.507%	$113.5901	$113.59	$113.60	$113.60
Purchase #2	$148.39	9.799%	$162.9307	$162.93	$162.95	$162.90
Purchase #3	$134.82	6.688%	$143.8368	$143.84	$143.85	$143.80
Purchase #4	$189.44	5.325%	$199.5277	$199.53	$199.55	$199.50
Purchase #5	$97.26	3.584%	$100.7458	$100.75	$100.75	$100.70
Purchase #6	$185.56	8.194%	$200.7648	$200.76	$200.75	$200.80
Purchase #7	$185.46	11.558%	$206.8955	$206.90	$206.90	$206.90
7 purchase totals =	$1,043.72		$1,128.2914	$1,128.30	$1,128.35	$1,128.20