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	$85.74	7.840%	$92.462	$92.46	$92.45	$92.50
Purchase #2	$199.27	5.652%	$210.5327	$210.53	$210.55	$210.50
Purchase #3	$72.52	11.414%	$80.7974	$80.80	$80.80	$80.80
Purchase #4	$200.30	3.210%	$206.7296	$206.73	$206.75	$206.70
Purchase #5	$141.72	9.198%	$154.7554	$154.76	$154.75	$154.80
Purchase #6	$142.75	9.847%	$156.8066	$156.81	$156.80	$156.80
Purchase #7	$105.99	5.218%	$111.5206	$111.52	$111.50	$111.50
7 purchase totals =	$948.29		$1,013.6043	$1,013.61	$1,013.60	$1,013.60