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	$161.26	9.745%	$176.9748	$176.97	$176.95	$177.00
Purchase #2	$130.91	11.349%	$145.767	$145.77	$145.75	$145.80
Purchase #3	$12.94	12.432%	$14.5487	$14.55	$14.55	$14.50
Purchase #4	$250.42	12.164%	$280.8811	$280.88	$280.90	$280.90
Purchase #5	$140.34	10.139%	$154.5691	$154.57	$154.55	$154.60
Purchase #6	$123.38	3.647%	$127.8797	$127.88	$127.90	$127.90
Purchase #7	$90.51	3.759%	$93.9123	$93.91	$93.90	$93.90
7 purchase totals =	$909.76		$994.5327	$994.53	$994.50	$994.60