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	$148.94	9.188%	$162.6246	$162.62	$162.60	$162.60
Purchase #2	$196.90	12.477%	$221.4672	$221.47	$221.45	$221.50
Purchase #3	$131.75	12.593%	$148.3413	$148.34	$148.35	$148.30
Purchase #4	$164.90	6.647%	$175.8609	$175.86	$175.85	$175.90
Purchase #5	$51.27	10.829%	$56.822	$56.82	$56.80	$56.80
Purchase #6	$89.71	5.850%	$94.958	$94.96	$94.95	$95.00
Purchase #7	$83.87	6.477%	$89.3023	$89.30	$89.30	$89.30
7 purchase totals =	$867.34		$949.3763	$949.37	$949.30	$949.40