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	$160.70	6.675%	$171.4267	$171.43	$171.45	$171.40
Purchase #2	$90.86	8.401%	$98.4931	$98.49	$98.50	$98.50
Purchase #3	$18.64	3.498%	$19.292	$19.29	$19.30	$19.30
Purchase #4	$145.31	7.442%	$156.124	$156.12	$156.10	$156.10
Purchase #5	$215.77	6.812%	$230.4683	$230.47	$230.45	$230.50
Purchase #6	$106.27	6.503%	$113.1807	$113.18	$113.20	$113.20
Purchase #7	$189.83	11.192%	$211.0758	$211.08	$211.10	$211.10
7 purchase totals =	$927.38		$1,000.0606	$1,000.06	$1,000.10	$1,000.10