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	$60.88	5.254%	$64.0786	$64.08	$64.10	$64.10
Purchase #2	$64.59	11.486%	$72.0088	$72.01	$72.00	$72.00
Purchase #3	$157.70	9.113%	$172.0712	$172.07	$172.05	$172.10
Purchase #4	$25.27	7.526%	$27.1718	$27.17	$27.15	$27.20
Purchase #5	$29.94	11.474%	$33.3753	$33.38	$33.40	$33.40
Purchase #6	$137.96	13.241%	$156.2273	$156.23	$156.25	$156.20
Purchase #7	$156.57	7.851%	$168.8623	$168.86	$168.85	$168.90
7 purchase totals =	$632.91		$693.7953	$693.80	$693.80	$693.90