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	$105.39	13.774%	$119.9064	$119.91	$119.90	$119.90
Purchase #2	$91.77	8.394%	$99.4732	$99.47	$99.45	$99.50
Purchase #3	$121.39	11.124%	$134.8934	$134.89	$134.90	$134.90
Purchase #4	$232.50	10.163%	$256.129	$256.13	$256.15	$256.10
Purchase #5	$76.28	9.178%	$83.281	$83.28	$83.30	$83.30
Purchase #6	$43.72	5.219%	$46.0017	$46.00	$46.00	$46.00
Purchase #7	$102.82	6.668%	$109.676	$109.68	$109.70	$109.70
7 purchase totals =	$773.87		$849.3607	$849.36	$849.40	$849.40