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	$76.85	11.350%	$85.5725	$85.57	$85.55	$85.60
Purchase #2	$55.81	4.223%	$58.1669	$58.17	$58.15	$58.20
Purchase #3	$106.39	4.671%	$111.3595	$111.36	$111.35	$111.40
Purchase #4	$217.53	3.722%	$225.6265	$225.63	$225.65	$225.60
Purchase #5	$91.57	8.716%	$99.5512	$99.55	$99.55	$99.60
Purchase #6	$78.46	5.657%	$82.8985	$82.90	$82.90	$82.90
Purchase #7	$80.87	10.360%	$89.2481	$89.25	$89.25	$89.20
7 purchase totals =	$707.48		$752.4232	$752.43	$752.40	$752.50