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	$37.27	12.413%	$41.8963	$41.90	$41.90	$41.90
Purchase #2	$226.99	3.182%	$234.2128	$234.21	$234.20	$234.20
Purchase #3	$208.83	6.159%	$221.6918	$221.69	$221.70	$221.70
Purchase #4	$80.54	13.440%	$91.3646	$91.36	$91.35	$91.40
Purchase #5	$150.89	13.139%	$170.7154	$170.72	$170.70	$170.70
Purchase #6	$89.42	5.788%	$94.5956	$94.60	$94.60	$94.60
Purchase #7	$185.59	7.648%	$199.7839	$199.78	$199.80	$199.80
7 purchase totals =	$979.53		$1,054.2604	$1,054.26	$1,054.25	$1,054.30