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	$142.61	7.136%	$152.7866	$152.79	$152.80	$152.80
Purchase #2	$42.58	7.722%	$45.868	$45.87	$45.85	$45.90
Purchase #3	$117.37	11.296%	$130.6281	$130.63	$130.65	$130.60
Purchase #4	$157.89	8.687%	$171.6059	$171.61	$171.60	$171.60
Purchase #5	$104.34	12.719%	$117.611	$117.61	$117.60	$117.60
Purchase #6	$6.57	3.859%	$6.8235	$6.82	$6.80	$6.80
Purchase #7	$147.60	10.127%	$162.5475	$162.55	$162.55	$162.50
7 purchase totals =	$718.96		$787.8706	$787.88	$787.85	$787.80