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	$74.65	7.363%	$80.1465	$80.15	$80.15	$80.10
Purchase #2	$90.50	9.300%	$98.9165	$98.92	$98.90	$98.90
Purchase #3	$239.57	7.737%	$258.1055	$258.11	$258.10	$258.10
Purchase #4	$94.45	11.262%	$105.087	$105.09	$105.10	$105.10
Purchase #5	$211.42	8.603%	$229.6085	$229.61	$229.60	$229.60
Purchase #6	$114.40	11.698%	$127.7825	$127.78	$127.80	$127.80
Purchase #7	$196.98	8.351%	$213.4298	$213.43	$213.45	$213.40
7 purchase totals =	$1,021.97		$1,113.0763	$1,113.09	$1,113.10	$1,113.00