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	$116.48	8.692%	$126.6044	$126.60	$126.60	$126.60
Purchase #2	$167.89	7.152%	$179.8975	$179.90	$179.90	$179.90
Purchase #3	$218.93	7.127%	$234.5331	$234.53	$234.55	$234.50
Purchase #4	$47.61	10.250%	$52.49	$52.49	$52.50	$52.50
Purchase #5	$95.63	4.705%	$100.1294	$100.13	$100.15	$100.10
Purchase #6	$96.65	7.344%	$103.748	$103.75	$103.75	$103.70
Purchase #7	$121.33	7.628%	$130.5851	$130.59	$130.60	$130.60
7 purchase totals =	$864.52		$927.9875	$927.99	$928.05	$927.90