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	$89.80	5.343%	$94.598	$94.60	$94.60	$94.60
Purchase #2	$88.71	9.217%	$96.8864	$96.89	$96.90	$96.90
Purchase #3	$100.63	6.798%	$107.4708	$107.47	$107.45	$107.50
Purchase #4	$71.87	9.173%	$78.4626	$78.46	$78.45	$78.50
Purchase #5	$70.59	10.346%	$77.8932	$77.89	$77.90	$77.90
Purchase #6	$242.48	5.866%	$256.7039	$256.70	$256.70	$256.70
Purchase #7	$102.44	7.730%	$110.3586	$110.36	$110.35	$110.40
7 purchase totals =	$766.52		$822.3735	$822.37	$822.35	$822.50