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	$23.52	4.755%	$24.6384	$24.64	$24.65	$24.60
Purchase #2	$85.94	10.694%	$95.1304	$95.13	$95.15	$95.10
Purchase #3	$118.74	11.763%	$132.7074	$132.71	$132.70	$132.70
Purchase #4	$23.60	9.815%	$25.9163	$25.92	$25.90	$25.90
Purchase #5	$16.25	6.546%	$17.3137	$17.31	$17.30	$17.30
Purchase #6	$57.43	3.289%	$59.3189	$59.32	$59.30	$59.30
Purchase #7	$143.57	4.866%	$150.5561	$150.56	$150.55	$150.60
7 purchase totals =	$469.05		$505.5812	$505.59	$505.55	$505.50