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	$69.31	11.873%	$77.5392	$77.54	$77.55	$77.50
Purchase #2	$208.94	13.134%	$236.3822	$236.38	$236.40	$236.40
Purchase #3	$142.89	8.783%	$155.44	$155.44	$155.45	$155.40
Purchase #4	$211.60	13.629%	$240.439	$240.44	$240.45	$240.40
Purchase #5	$29.48	8.501%	$31.9861	$31.99	$32.00	$32.00
Purchase #6	$78.61	7.581%	$84.5694	$84.57	$84.55	$84.60
Purchase #7	$237.29	7.658%	$255.4617	$255.46	$255.45	$255.50
7 purchase totals =	$978.12		$1,081.8176	$1,081.82	$1,081.85	$1,081.80