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	$10.50	6.821%	$11.2162	$11.22	$11.20	$11.20
Purchase #2	$62.89	11.164%	$69.911	$69.91	$69.90	$69.90
Purchase #3	$114.85	10.867%	$127.3307	$127.33	$127.35	$127.30
Purchase #4	$196.56	3.769%	$203.9683	$203.97	$203.95	$204.00
Purchase #5	$192.86	6.580%	$205.5502	$205.55	$205.55	$205.60
Purchase #6	$62.27	3.425%	$64.4027	$64.40	$64.40	$64.40
Purchase #7	$18.81	9.171%	$20.5351	$20.54	$20.55	$20.50
7 purchase totals =	$658.74		$702.9142	$702.92	$702.90	$702.90