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	$126.97	4.172%	$132.2672	$132.27	$132.25	$132.30
Purchase #2	$111.83	8.398%	$121.2215	$121.22	$121.20	$121.20
Purchase #3	$97.88	6.716%	$104.4536	$104.45	$104.45	$104.50
Purchase #4	$51.75	6.802%	$55.27	$55.27	$55.25	$55.30
Purchase #5	$10.92	6.541%	$11.6343	$11.63	$11.65	$11.60
Purchase #6	$141.83	4.296%	$147.923	$147.92	$147.90	$147.90
Purchase #7	$92.61	7.729%	$99.7678	$99.77	$99.75	$99.80
7 purchase totals =	$633.79		$672.5374	$672.53	$672.45	$672.60