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	$97.37	5.431%	$102.6582	$102.66	$102.65	$102.70
Purchase #2	$242.94	11.750%	$271.4855	$271.49	$271.50	$271.50
Purchase #3	$229.76	11.259%	$255.6287	$255.63	$255.65	$255.60
Purchase #4	$246.86	12.743%	$278.3174	$278.32	$278.30	$278.30
Purchase #5	$50.95	4.561%	$53.2738	$53.27	$53.25	$53.30
Purchase #6	$121.43	4.684%	$127.1178	$127.12	$127.10	$127.10
Purchase #7	$127.92	11.547%	$142.6909	$142.69	$142.70	$142.70
7 purchase totals =	$1,117.23		$1,231.1723	$1,231.18	$1,231.15	$1,231.20