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	$118.70	11.427%	$132.2638	$132.26	$132.25	$132.30
Purchase #2	$18.77	8.140%	$20.2979	$20.30	$20.30	$20.30
Purchase #3	$232.61	10.296%	$256.5595	$256.56	$256.55	$256.60
Purchase #4	$67.94	12.607%	$76.5052	$76.51	$76.50	$76.50
Purchase #5	$232.71	13.555%	$264.2538	$264.25	$264.25	$264.30
Purchase #6	$35.74	5.312%	$37.6385	$37.64	$37.65	$37.60
Purchase #7	$86.99	6.755%	$92.8662	$92.87	$92.85	$92.90
7 purchase totals =	$793.46		$880.3849	$880.39	$880.35	$880.50