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	$38.47	7.517%	$41.3618	$41.36	$41.35	$41.40
Purchase #2	$196.54	9.509%	$215.229	$215.23	$215.25	$215.20
Purchase #3	$236.44	12.102%	$265.054	$265.05	$265.05	$265.10
Purchase #4	$195.53	7.185%	$209.5788	$209.58	$209.60	$209.60
Purchase #5	$43.87	6.577%	$46.7553	$46.76	$46.75	$46.80
Purchase #6	$61.35	10.223%	$67.6218	$67.62	$67.60	$67.60
Purchase #7	$12.52	11.500%	$13.9598	$13.96	$13.95	$14.00
7 purchase totals =	$784.72		$859.5605	$859.56	$859.55	$859.70