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	$105.38	5.508%	$111.1843	$111.18	$111.20	$111.20
Purchase #2	$130.57	5.341%	$137.5437	$137.54	$137.55	$137.50
Purchase #3	$228.54	7.528%	$245.7445	$245.74	$245.75	$245.70
Purchase #4	$172.88	8.611%	$187.7667	$187.77	$187.75	$187.80
Purchase #5	$179.37	6.430%	$190.9035	$190.90	$190.90	$190.90
Purchase #6	$73.73	11.726%	$82.3756	$82.38	$82.40	$82.40
Purchase #7	$167.83	4.237%	$174.941	$174.94	$174.95	$174.90
7 purchase totals =	$1,058.30		$1,130.4593	$1,130.45	$1,130.50	$1,130.40