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	$120.97	5.665%	$127.823	$127.82	$127.80	$127.80
Purchase #2	$33.46	11.229%	$37.2172	$37.22	$37.20	$37.20
Purchase #3	$179.34	5.289%	$188.8253	$188.83	$188.85	$188.80
Purchase #4	$33.84	4.686%	$35.4257	$35.43	$35.45	$35.40
Purchase #5	$25.27	8.650%	$27.4559	$27.46	$27.45	$27.50
Purchase #6	$195.81	4.223%	$204.0791	$204.08	$204.10	$204.10
Purchase #7	$31.31	11.711%	$34.9767	$34.98	$35.00	$35.00
7 purchase totals =	$620.00		$655.8029	$655.82	$655.85	$655.80