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	$91.34	11.459%	$101.8067	$101.81	$101.80	$101.80
Purchase #2	$238.91	9.365%	$261.2839	$261.28	$261.30	$261.30
Purchase #3	$233.79	9.588%	$256.2058	$256.21	$256.20	$256.20
Purchase #4	$56.85	8.133%	$61.4736	$61.47	$61.45	$61.50
Purchase #5	$189.87	3.674%	$196.8458	$196.85	$196.85	$196.80
Purchase #6	$116.75	13.277%	$132.2509	$132.25	$132.25	$132.30
Purchase #7	$105.62	6.341%	$112.3174	$112.32	$112.30	$112.30
7 purchase totals =	$1,033.13		$1,122.1841	$1,122.19	$1,122.15	$1,122.20