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	$150.55	9.347%	$164.6219	$164.62	$164.60	$164.60
Purchase #2	$49.41	8.638%	$53.678	$53.68	$53.70	$53.70
Purchase #3	$206.29	13.674%	$234.4981	$234.50	$234.50	$234.50
Purchase #4	$190.38	10.446%	$210.2671	$210.27	$210.25	$210.30
Purchase #5	$39.41	5.557%	$41.6	$41.60	$41.60	$41.60
Purchase #6	$91.56	7.380%	$98.3171	$98.32	$98.30	$98.30
Purchase #7	$44.50	9.820%	$48.8699	$48.87	$48.85	$48.90
7 purchase totals =	$772.10		$851.8521	$851.86	$851.80	$851.90