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	$102.59	8.266%	$111.0701	$111.07	$111.05	$111.10
Purchase #2	$62.98	12.451%	$70.8216	$70.82	$70.80	$70.80
Purchase #3	$135.43	12.379%	$152.1949	$152.19	$152.20	$152.20
Purchase #4	$146.53	10.852%	$162.4314	$162.43	$162.45	$162.40
Purchase #5	$73.48	7.254%	$78.8102	$78.81	$78.80	$78.80
Purchase #6	$179.40	7.369%	$192.62	$192.62	$192.60	$192.60
Purchase #7	$86.26	9.772%	$94.6893	$94.69	$94.70	$94.70
7 purchase totals =	$786.67		$862.6375	$862.63	$862.60	$862.60