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	$86.66	3.593%	$89.7737	$89.77	$89.75	$89.80
Purchase #2	$118.38	7.622%	$127.4029	$127.40	$127.40	$127.40
Purchase #3	$109.96	3.105%	$113.3743	$113.37	$113.35	$113.40
Purchase #4	$161.82	6.488%	$172.3189	$172.32	$172.30	$172.30
Purchase #5	$18.74	7.813%	$20.2042	$20.20	$20.20	$20.20
Purchase #6	$33.74	7.603%	$36.3053	$36.31	$36.30	$36.30
Purchase #7	$181.82	12.707%	$204.9239	$204.92	$204.90	$204.90
7 purchase totals =	$711.12		$764.3032	$764.29	$764.20	$764.30