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	$81.43	11.778%	$91.0208	$91.02	$91.00	$91.00
Purchase #2	$28.71	9.707%	$31.4969	$31.50	$31.50	$31.50
Purchase #3	$62.39	8.709%	$67.8235	$67.82	$67.80	$67.80
Purchase #4	$42.88	4.522%	$44.819	$44.82	$44.80	$44.80
Purchase #5	$38.71	9.571%	$42.4149	$42.41	$42.40	$42.40
Purchase #6	$32.28	4.712%	$33.801	$33.80	$33.80	$33.80
Purchase #7	$42.38	13.159%	$47.9568	$47.96	$47.95	$48.00
7 purchase totals =	$328.78		$359.3329	$359.33	$359.25	$359.30