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	$83.79	10.338%	$92.4522	$92.45	$92.45	$92.50
Purchase #2	$137.44	3.866%	$142.7534	$142.75	$142.75	$142.80
Purchase #3	$204.27	7.245%	$219.0694	$219.07	$219.05	$219.10
Purchase #4	$106.67	4.468%	$111.436	$111.44	$111.45	$111.40
Purchase #5	$246.71	6.802%	$263.4912	$263.49	$263.50	$263.50
Purchase #6	$86.83	4.115%	$90.4031	$90.40	$90.40	$90.40
Purchase #7	$57.58	10.194%	$63.4497	$63.45	$63.45	$63.40
7 purchase totals =	$923.29		$983.0550	$983.05	$983.05	$983.10