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	$66.27	5.296%	$69.7797	$69.78	$69.80	$69.80
Purchase #2	$82.89	10.712%	$91.7692	$91.77	$91.75	$91.80
Purchase #3	$49.40	9.158%	$53.9241	$53.92	$53.90	$53.90
Purchase #4	$226.29	13.164%	$256.0788	$256.08	$256.10	$256.10
Purchase #5	$154.27	9.713%	$169.2542	$169.25	$169.25	$169.30
Purchase #6	$226.98	3.132%	$234.089	$234.09	$234.10	$234.10
Purchase #7	$124.72	13.705%	$141.8129	$141.81	$141.80	$141.80
7 purchase totals =	$930.82		$1,016.7079	$1,016.70	$1,016.70	$1,016.80