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	$82.93	7.764%	$89.3687	$89.37	$89.35	$89.40
Purchase #2	$85.96	6.575%	$91.6119	$91.61	$91.60	$91.60
Purchase #3	$153.66	7.775%	$165.6071	$165.61	$165.60	$165.60
Purchase #4	$195.41	9.168%	$213.3252	$213.33	$213.35	$213.30
Purchase #5	$221.46	12.594%	$249.3507	$249.35	$249.35	$249.40
Purchase #6	$230.82	11.357%	$257.0342	$257.03	$257.05	$257.00
Purchase #7	$29.94	3.637%	$31.0289	$31.03	$31.05	$31.00
7 purchase totals =	$1,000.18		$1,097.3267	$1,097.33	$1,097.35	$1,097.30