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	$220.35	8.285%	$238.606	$238.61	$238.60	$238.60
Purchase #2	$50.83	7.260%	$54.5203	$54.52	$54.50	$54.50
Purchase #3	$162.59	11.618%	$181.4797	$181.48	$181.50	$181.50
Purchase #4	$156.79	9.357%	$171.4608	$171.46	$171.45	$171.50
Purchase #5	$141.88	3.638%	$147.0416	$147.04	$147.05	$147.00
Purchase #6	$36.46	6.633%	$38.8784	$38.88	$38.90	$38.90
Purchase #7	$243.63	13.117%	$275.5869	$275.59	$275.60	$275.60
7 purchase totals =	$1,012.53		$1,107.5737	$1,107.58	$1,107.60	$1,107.60