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	$156.32	10.325%	$172.46	$172.46	$172.45	$172.50
Purchase #2	$87.47	12.711%	$98.5883	$98.59	$98.60	$98.60
Purchase #3	$64.66	9.617%	$70.8784	$70.88	$70.90	$70.90
Purchase #4	$243.29	5.318%	$256.2282	$256.23	$256.25	$256.20
Purchase #5	$237.63	13.581%	$269.9025	$269.90	$269.90	$269.90
Purchase #6	$151.64	12.801%	$171.0514	$171.05	$171.05	$171.10
Purchase #7	$210.32	11.538%	$234.5867	$234.59	$234.60	$234.60
7 purchase totals =	$1,151.33		$1,273.6955	$1,273.70	$1,273.75	$1,273.80