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	$96.63	4.545%	$101.0218	$101.02	$101.00	$101.00
Purchase #2	$66.98	8.678%	$72.7925	$72.79	$72.80	$72.80
Purchase #3	$144.62	9.475%	$158.3227	$158.32	$158.30	$158.30
Purchase #4	$170.88	6.395%	$181.8078	$181.81	$181.80	$181.80
Purchase #5	$243.36	12.647%	$274.1377	$274.14	$274.15	$274.10
Purchase #6	$114.65	11.372%	$127.688	$127.69	$127.70	$127.70
Purchase #7	$31.36	12.340%	$35.2298	$35.23	$35.25	$35.20
7 purchase totals =	$868.48		$951.0003	$951.00	$951.00	$950.90