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	$58.76	4.582%	$61.4524	$61.45	$61.45	$61.50
Purchase #2	$41.71	10.228%	$45.9761	$45.98	$46.00	$46.00
Purchase #3	$63.58	6.305%	$67.5887	$67.59	$67.60	$67.60
Purchase #4	$137.76	6.628%	$146.8907	$146.89	$146.90	$146.90
Purchase #5	$159.89	3.776%	$165.9274	$165.93	$165.95	$165.90
Purchase #6	$119.76	4.524%	$125.1779	$125.18	$125.20	$125.20
Purchase #7	$183.96	12.731%	$207.3799	$207.38	$207.40	$207.40
7 purchase totals =	$765.42		$820.3931	$820.40	$820.50	$820.50