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	$168.74	12.690%	$190.1531	$190.15	$190.15	$190.20
Purchase #2	$23.35	9.766%	$25.6304	$25.63	$25.65	$25.60
Purchase #3	$31.26	10.747%	$34.6195	$34.62	$34.60	$34.60
Purchase #4	$127.80	7.848%	$137.8297	$137.83	$137.85	$137.80
Purchase #5	$200.39	5.107%	$210.6239	$210.62	$210.60	$210.60
Purchase #6	$176.33	5.159%	$185.4269	$185.43	$185.45	$185.40
Purchase #7	$111.51	4.223%	$116.2191	$116.22	$116.20	$116.20
7 purchase totals =	$839.38		$900.5026	$900.50	$900.50	$900.40