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	$71.36	4.415%	$74.5105	$74.51	$74.50	$74.50
Purchase #2	$71.94	3.694%	$74.5975	$74.60	$74.60	$74.60
Purchase #3	$133.94	13.845%	$152.484	$152.48	$152.50	$152.50
Purchase #4	$43.29	5.628%	$45.7264	$45.73	$45.75	$45.70
Purchase #5	$211.55	3.630%	$219.2293	$219.23	$219.25	$219.20
Purchase #6	$43.44	4.823%	$45.5351	$45.54	$45.55	$45.50
Purchase #7	$154.29	3.570%	$159.7982	$159.80	$159.80	$159.80
7 purchase totals =	$729.81		$771.8810	$771.89	$771.95	$771.80