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	$241.63	13.240%	$273.6218	$273.62	$273.60	$273.60
Purchase #2	$152.49	10.747%	$168.8781	$168.88	$168.90	$168.90
Purchase #3	$60.86	11.144%	$67.6422	$67.64	$67.65	$67.60
Purchase #4	$109.30	12.741%	$123.2259	$123.23	$123.25	$123.20
Purchase #5	$205.49	3.665%	$213.0212	$213.02	$213.00	$213.00
Purchase #6	$133.98	5.419%	$141.2404	$141.24	$141.25	$141.20
Purchase #7	$152.46	3.243%	$157.4043	$157.40	$157.40	$157.40
7 purchase totals =	$1,056.21		$1,145.0339	$1,145.03	$1,145.05	$1,144.90