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	$93.75	12.650%	$105.6094	$105.61	$105.60	$105.60
Purchase #2	$89.93	11.239%	$100.0372	$100.04	$100.05	$100.00
Purchase #3	$151.25	5.600%	$159.72	$159.72	$159.70	$159.70
Purchase #4	$92.99	3.304%	$96.0624	$96.06	$96.05	$96.10
Purchase #5	$143.52	12.227%	$161.0682	$161.07	$161.05	$161.10
Purchase #6	$35.90	5.193%	$37.7643	$37.76	$37.75	$37.80
Purchase #7	$170.35	12.353%	$191.3933	$191.39	$191.40	$191.40
7 purchase totals =	$777.69		$851.6548	$851.65	$851.60	$851.70