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	$135.95	4.452%	$142.0025	$142.00	$142.00	$142.00
Purchase #2	$31.32	3.738%	$32.4907	$32.49	$32.50	$32.50
Purchase #3	$62.44	8.200%	$67.5601	$67.56	$67.55	$67.60
Purchase #4	$177.74	6.830%	$189.8796	$189.88	$189.90	$189.90
Purchase #5	$153.49	13.640%	$174.426	$174.43	$174.45	$174.40
Purchase #6	$42.49	4.678%	$44.4777	$44.48	$44.50	$44.50
Purchase #7	$20.84	3.452%	$21.5594	$21.56	$21.55	$21.60
7 purchase totals =	$624.27		$672.3960	$672.40	$672.45	$672.50