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	$110.61	5.716%	$116.9325	$116.93	$116.95	$116.90
Purchase #2	$34.55	10.216%	$38.0796	$38.08	$38.10	$38.10
Purchase #3	$116.77	9.353%	$127.6915	$127.69	$127.70	$127.70
Purchase #4	$123.39	13.779%	$140.3919	$140.39	$140.40	$140.40
Purchase #5	$185.69	3.833%	$192.8075	$192.81	$192.80	$192.80
Purchase #6	$186.30	7.824%	$200.8761	$200.88	$200.90	$200.90
Purchase #7	$196.56	3.403%	$203.2489	$203.25	$203.25	$203.20
7 purchase totals =	$953.87		$1,020.0280	$1,020.03	$1,020.10	$1,020.00