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	$117.31	10.777%	$129.9525	$129.95	$129.95	$130.00
Purchase #2	$83.84	6.528%	$89.3131	$89.31	$89.30	$89.30
Purchase #3	$154.75	13.377%	$175.4509	$175.45	$175.45	$175.50
Purchase #4	$146.28	11.111%	$162.5332	$162.53	$162.55	$162.50
Purchase #5	$202.28	10.874%	$224.2759	$224.28	$224.30	$224.30
Purchase #6	$43.31	8.218%	$46.8692	$46.87	$46.85	$46.90
Purchase #7	$32.83	12.406%	$36.9029	$36.90	$36.90	$36.90
7 purchase totals =	$780.60		$865.2977	$865.29	$865.30	$865.40