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	$38.38	12.779%	$43.2846	$43.28	$43.30	$43.30
Purchase #2	$206.69	7.480%	$222.1504	$222.15	$222.15	$222.20
Purchase #3	$111.64	8.126%	$120.7119	$120.71	$120.70	$120.70
Purchase #4	$245.59	13.751%	$279.3611	$279.36	$279.35	$279.40
Purchase #5	$147.76	3.148%	$152.4115	$152.41	$152.40	$152.40
Purchase #6	$106.93	13.111%	$120.9496	$120.95	$120.95	$120.90
Purchase #7	$110.33	8.324%	$119.5139	$119.51	$119.50	$119.50
7 purchase totals =	$967.32		$1,058.3830	$1,058.37	$1,058.35	$1,058.40