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	$99.54	5.852%	$105.3651	$105.37	$105.35	$105.40
Purchase #2	$80.97	4.471%	$84.5902	$84.59	$84.60	$84.60
Purchase #3	$100.76	13.684%	$114.548	$114.55	$114.55	$114.50
Purchase #4	$246.30	11.812%	$275.393	$275.39	$275.40	$275.40
Purchase #5	$39.82	4.474%	$41.6015	$41.60	$41.60	$41.60
Purchase #6	$233.70	12.112%	$262.0057	$262.01	$262.00	$262.00
Purchase #7	$73.75	9.190%	$80.5276	$80.53	$80.55	$80.50
7 purchase totals =	$874.84		$964.0311	$964.04	$964.05	$964.00