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	$59.64	7.343%	$64.0194	$64.02	$64.00	$64.00
Purchase #2	$249.57	13.659%	$283.6588	$283.66	$283.65	$283.70
Purchase #3	$178.97	8.278%	$193.7851	$193.79	$193.80	$193.80
Purchase #4	$84.88	5.779%	$89.7852	$89.79	$89.80	$89.80
Purchase #5	$240.40	12.589%	$270.664	$270.66	$270.65	$270.70
Purchase #6	$95.77	5.322%	$100.8669	$100.87	$100.85	$100.90
Purchase #7	$78.49	6.682%	$83.7347	$83.73	$83.75	$83.70
7 purchase totals =	$987.72		$1,086.5141	$1,086.52	$1,086.50	$1,086.60