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	$79.41	10.523%	$87.7663	$87.77	$87.75	$87.80
Purchase #2	$218.40	4.282%	$227.7519	$227.75	$227.75	$227.80
Purchase #3	$17.51	7.281%	$18.7849	$18.78	$18.80	$18.80
Purchase #4	$109.75	8.303%	$118.8625	$118.86	$118.85	$118.90
Purchase #5	$13.25	3.179%	$13.6712	$13.67	$13.65	$13.70
Purchase #6	$111.76	3.834%	$116.0449	$116.04	$116.05	$116.00
Purchase #7	$162.51	3.702%	$168.5261	$168.53	$168.55	$168.50
7 purchase totals =	$712.59		$751.4078	$751.40	$751.40	$751.50