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	$160.60	4.840%	$168.373	$168.37	$168.35	$168.40
Purchase #2	$68.55	5.254%	$72.1516	$72.15	$72.15	$72.20
Purchase #3	$218.79	4.155%	$227.8807	$227.88	$227.90	$227.90
Purchase #4	$28.82	13.549%	$32.7248	$32.72	$32.70	$32.70
Purchase #5	$192.57	5.339%	$202.8513	$202.85	$202.85	$202.90
Purchase #6	$205.37	3.489%	$212.5354	$212.54	$212.55	$212.50
Purchase #7	$19.58	6.177%	$20.7895	$20.79	$20.80	$20.80
7 purchase totals =	$894.28		$937.3063	$937.30	$937.30	$937.40