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	$75.99	13.774%	$86.4569	$86.46	$86.45	$86.50
Purchase #2	$194.85	9.123%	$212.6262	$212.63	$212.65	$212.60
Purchase #3	$42.83	8.780%	$46.5905	$46.59	$46.60	$46.60
Purchase #4	$36.79	11.185%	$40.905	$40.91	$40.90	$40.90
Purchase #5	$35.33	4.770%	$37.0152	$37.02	$37.00	$37.00
Purchase #6	$113.78	4.502%	$118.9024	$118.90	$118.90	$118.90
Purchase #7	$59.71	12.460%	$67.1499	$67.15	$67.15	$67.10
7 purchase totals =	$559.28		$609.6461	$609.66	$609.65	$609.60