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	$55.68	10.522%	$61.5386	$61.54	$61.55	$61.50
Purchase #2	$136.69	12.349%	$153.5698	$153.57	$153.55	$153.60
Purchase #3	$113.36	12.179%	$127.1661	$127.17	$127.15	$127.20
Purchase #4	$210.59	8.653%	$228.8124	$228.81	$228.80	$228.80
Purchase #5	$206.90	7.425%	$222.2623	$222.26	$222.25	$222.30
Purchase #6	$187.60	8.501%	$203.5479	$203.55	$203.55	$203.50
Purchase #7	$141.78	6.146%	$150.4938	$150.49	$150.50	$150.50
7 purchase totals =	$1,052.60		$1,147.3909	$1,147.39	$1,147.35	$1,147.40