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	$164.35	11.356%	$183.0136	$183.01	$183.00	$183.00
Purchase #2	$98.37	6.345%	$104.6116	$104.61	$104.60	$104.60
Purchase #3	$135.91	9.287%	$148.532	$148.53	$148.55	$148.50
Purchase #4	$145.68	13.508%	$165.3585	$165.36	$165.35	$165.40
Purchase #5	$14.37	3.680%	$14.8988	$14.90	$14.90	$14.90
Purchase #6	$174.60	12.511%	$196.4442	$196.44	$196.45	$196.40
Purchase #7	$188.59	5.750%	$199.4339	$199.43	$199.45	$199.40
7 purchase totals =	$921.87		$1,012.2926	$1,012.28	$1,012.30	$1,012.20