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	$110.51	6.245%	$117.4113	$117.41	$117.40	$117.40
Purchase #2	$90.55	11.151%	$100.6472	$100.65	$100.65	$100.60
Purchase #3	$123.76	4.308%	$129.0916	$129.09	$129.10	$129.10
Purchase #4	$177.61	12.801%	$200.3459	$200.35	$200.35	$200.30
Purchase #5	$135.64	8.811%	$147.5912	$147.59	$147.60	$147.60
Purchase #6	$138.97	13.671%	$157.9686	$157.97	$157.95	$158.00
Purchase #7	$160.53	3.506%	$166.1582	$166.16	$166.15	$166.20
7 purchase totals =	$937.57		$1,019.2140	$1,019.22	$1,019.20	$1,019.20