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	$198.66	4.791%	$208.1778	$208.18	$208.20	$208.20
Purchase #2	$246.49	6.153%	$261.6565	$261.66	$261.65	$261.70
Purchase #3	$72.71	13.798%	$82.7425	$82.74	$82.75	$82.70
Purchase #4	$34.78	7.738%	$37.4713	$37.47	$37.45	$37.50
Purchase #5	$233.57	5.290%	$245.9259	$245.93	$245.95	$245.90
Purchase #6	$69.77	12.685%	$78.6203	$78.62	$78.60	$78.60
Purchase #7	$198.41	6.838%	$211.9773	$211.98	$212.00	$212.00
7 purchase totals =	$1,054.39		$1,126.5716	$1,126.58	$1,126.60	$1,126.60