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	$218.31	9.412%	$238.8573	$238.86	$238.85	$238.90
Purchase #2	$65.37	11.378%	$72.8078	$72.81	$72.80	$72.80
Purchase #3	$31.60	6.375%	$33.6145	$33.61	$33.60	$33.60
Purchase #4	$9.60	13.137%	$10.8612	$10.86	$10.85	$10.90
Purchase #5	$161.79	12.427%	$181.8956	$181.90	$181.90	$181.90
Purchase #6	$223.56	10.176%	$246.3095	$246.31	$246.30	$246.30
Purchase #7	$179.71	13.528%	$204.0212	$204.02	$204.00	$204.00
7 purchase totals =	$889.94		$988.3671	$988.37	$988.30	$988.40