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	$9.90	10.705%	$10.9598	$10.96	$10.95	$11.00
Purchase #2	$144.41	9.707%	$158.4279	$158.43	$158.45	$158.40
Purchase #3	$34.73	5.189%	$36.5321	$36.53	$36.55	$36.50
Purchase #4	$160.82	11.269%	$178.9428	$178.94	$178.95	$178.90
Purchase #5	$133.33	13.111%	$150.8109	$150.81	$150.80	$150.80
Purchase #6	$33.97	10.198%	$37.4343	$37.43	$37.45	$37.40
Purchase #7	$249.43	12.849%	$281.4793	$281.48	$281.50	$281.50
7 purchase totals =	$766.59		$854.5871	$854.58	$854.65	$854.50