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	$127.78	12.816%	$144.1563	$144.16	$144.15	$144.20
Purchase #2	$196.37	13.647%	$223.1686	$223.17	$223.15	$223.20
Purchase #3	$18.49	10.406%	$20.4141	$20.41	$20.40	$20.40
Purchase #4	$168.83	3.198%	$174.2292	$174.23	$174.25	$174.20
Purchase #5	$178.57	10.241%	$196.8574	$196.86	$196.85	$196.90
Purchase #6	$214.89	13.171%	$243.1932	$243.19	$243.20	$243.20
Purchase #7	$34.88	5.569%	$36.8225	$36.82	$36.80	$36.80
7 purchase totals =	$939.81		$1,038.8413	$1,038.84	$1,038.80	$1,038.90