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	$211.33	13.855%	$240.6098	$240.61	$240.60	$240.60
Purchase #2	$58.31	3.684%	$60.4581	$60.46	$60.45	$60.50
Purchase #3	$151.67	9.618%	$166.2576	$166.26	$166.25	$166.30
Purchase #4	$69.94	12.415%	$78.6231	$78.62	$78.60	$78.60
Purchase #5	$238.77	8.361%	$258.7336	$258.73	$258.75	$258.70
Purchase #6	$176.94	6.692%	$188.7808	$188.78	$188.80	$188.80
Purchase #7	$189.73	4.271%	$197.8334	$197.83	$197.85	$197.80
7 purchase totals =	$1,096.69		$1,191.2964	$1,191.29	$1,191.30	$1,191.30