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	$11.44	4.338%	$11.9363	$11.94	$11.95	$11.90
Purchase #2	$208.94	4.211%	$217.7385	$217.74	$217.75	$217.70
Purchase #3	$198.79	3.870%	$206.4832	$206.48	$206.50	$206.50
Purchase #4	$67.89	5.564%	$71.6674	$71.67	$71.65	$71.70
Purchase #5	$97.33	13.692%	$110.6564	$110.66	$110.65	$110.70
Purchase #6	$211.72	12.802%	$238.8244	$238.82	$238.80	$238.80
Purchase #7	$221.87	9.814%	$243.6443	$243.64	$243.65	$243.60
7 purchase totals =	$1,017.98		$1,100.9505	$1,100.95	$1,100.95	$1,100.90