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	$140.68	12.268%	$157.9386	$157.94	$157.95	$157.90
Purchase #2	$69.70	12.425%	$78.3602	$78.36	$78.35	$78.40
Purchase #3	$124.71	3.722%	$129.3517	$129.35	$129.35	$129.40
Purchase #4	$78.89	4.271%	$82.2594	$82.26	$82.25	$82.30
Purchase #5	$40.99	10.776%	$45.4071	$45.41	$45.40	$45.40
Purchase #6	$123.75	6.553%	$131.8593	$131.86	$131.85	$131.90
Purchase #7	$100.26	3.470%	$103.739	$103.74	$103.75	$103.70
7 purchase totals =	$678.98		$728.9153	$728.92	$728.90	$729.00