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	$187.39	11.626%	$209.176	$209.18	$209.20	$209.20
Purchase #2	$64.41	9.178%	$70.3215	$70.32	$70.30	$70.30
Purchase #3	$120.65	8.840%	$131.3155	$131.32	$131.30	$131.30
Purchase #4	$212.30	5.418%	$223.8024	$223.80	$223.80	$223.80
Purchase #5	$109.89	4.517%	$114.8537	$114.85	$114.85	$114.90
Purchase #6	$170.32	12.524%	$191.6509	$191.65	$191.65	$191.70
Purchase #7	$62.93	5.778%	$66.5661	$66.57	$66.55	$66.60
7 purchase totals =	$927.89		$1,007.6861	$1,007.69	$1,007.65	$1,007.80