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	$204.89	8.593%	$222.4962	$222.50	$222.50	$222.50
Purchase #2	$144.97	12.198%	$162.6534	$162.65	$162.65	$162.70
Purchase #3	$198.41	6.378%	$211.0646	$211.06	$211.05	$211.10
Purchase #4	$61.39	6.672%	$65.4859	$65.49	$65.50	$65.50
Purchase #5	$189.82	10.144%	$209.0753	$209.08	$209.10	$209.10
Purchase #6	$196.96	12.811%	$222.1925	$222.19	$222.20	$222.20
Purchase #7	$249.59	6.497%	$265.8059	$265.81	$265.80	$265.80
7 purchase totals =	$1,246.03		$1,358.7738	$1,358.78	$1,358.80	$1,358.90