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	$160.55	5.610%	$169.5569	$169.56	$169.55	$169.60
Purchase #2	$11.60	13.566%	$13.1737	$13.17	$13.15	$13.20
Purchase #3	$212.85	8.715%	$231.3999	$231.40	$231.40	$231.40
Purchase #4	$57.84	11.282%	$64.3655	$64.37	$64.35	$64.40
Purchase #5	$185.60	7.189%	$198.9428	$198.94	$198.95	$198.90
Purchase #6	$47.69	11.667%	$53.254	$53.25	$53.25	$53.30
Purchase #7	$137.52	10.700%	$152.2346	$152.23	$152.25	$152.20
7 purchase totals =	$813.65		$882.9274	$882.92	$882.90	$883.00