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	$232.56	10.514%	$257.0114	$257.01	$257.00	$257.00
Purchase #2	$38.94	9.474%	$42.6292	$42.63	$42.65	$42.60
Purchase #3	$81.85	7.663%	$88.1222	$88.12	$88.10	$88.10
Purchase #4	$66.70	8.136%	$72.1267	$72.13	$72.15	$72.10
Purchase #5	$173.27	13.342%	$196.3877	$196.39	$196.40	$196.40
Purchase #6	$186.60	6.406%	$198.5536	$198.55	$198.55	$198.60
Purchase #7	$200.52	11.557%	$223.6941	$223.69	$223.70	$223.70
7 purchase totals =	$980.44		$1,078.5249	$1,078.52	$1,078.55	$1,078.50