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	$160.89	9.580%	$176.3033	$176.30	$176.30	$176.30
Purchase #2	$73.65	7.108%	$78.885	$78.89	$78.90	$78.90
Purchase #3	$80.94	4.511%	$84.5912	$84.59	$84.60	$84.60
Purchase #4	$210.36	7.173%	$225.4491	$225.45	$225.45	$225.40
Purchase #5	$150.28	6.177%	$159.5628	$159.56	$159.55	$159.60
Purchase #6	$111.56	12.472%	$125.4738	$125.47	$125.45	$125.50
Purchase #7	$192.55	6.249%	$204.5824	$204.58	$204.60	$204.60
7 purchase totals =	$980.23		$1,054.8476	$1,054.84	$1,054.85	$1,054.90