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	$132.49	10.405%	$146.2756	$146.28	$146.30	$146.30
Purchase #2	$56.54	5.394%	$59.5898	$59.59	$59.60	$59.60
Purchase #3	$131.75	8.424%	$142.8486	$142.85	$142.85	$142.80
Purchase #4	$144.51	5.809%	$152.9046	$152.90	$152.90	$152.90
Purchase #5	$194.35	12.595%	$218.8284	$218.83	$218.85	$218.80
Purchase #6	$119.27	4.478%	$124.6109	$124.61	$124.60	$124.60
Purchase #7	$88.47	8.840%	$96.2907	$96.29	$96.30	$96.30
7 purchase totals =	$867.38		$941.3486	$941.35	$941.40	$941.30