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	$211.89	6.330%	$225.3026	$225.30	$225.30	$225.30
Purchase #2	$15.68	7.112%	$16.7952	$16.80	$16.80	$16.80
Purchase #3	$123.49	11.176%	$137.2912	$137.29	$137.30	$137.30
Purchase #4	$166.28	11.597%	$185.5635	$185.56	$185.55	$185.60
Purchase #5	$90.30	6.276%	$95.9672	$95.97	$95.95	$96.00
Purchase #6	$81.79	4.676%	$85.6145	$85.61	$85.60	$85.60
Purchase #7	$70.82	10.348%	$78.1485	$78.15	$78.15	$78.10
7 purchase totals =	$760.25		$824.6827	$824.68	$824.65	$824.70