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	$216.95	11.233%	$241.32	$241.32	$241.30	$241.30
Purchase #2	$227.93	5.470%	$240.3978	$240.40	$240.40	$240.40
Purchase #3	$28.89	9.187%	$31.5441	$31.54	$31.55	$31.50
Purchase #4	$9.57	5.328%	$10.0799	$10.08	$10.10	$10.10
Purchase #5	$167.33	13.501%	$189.9212	$189.92	$189.90	$189.90
Purchase #6	$123.29	9.375%	$134.8484	$134.85	$134.85	$134.80
Purchase #7	$204.90	12.858%	$231.246	$231.25	$231.25	$231.20
7 purchase totals =	$978.86		$1,079.3574	$1,079.36	$1,079.35	$1,079.20