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	$163.96	5.788%	$173.45	$173.45	$173.45	$173.50
Purchase #2	$167.84	8.428%	$181.9856	$181.99	$182.00	$182.00
Purchase #3	$42.57	13.397%	$48.2731	$48.27	$48.25	$48.30
Purchase #4	$155.85	13.275%	$176.5391	$176.54	$176.55	$176.50
Purchase #5	$175.33	11.712%	$195.8646	$195.86	$195.85	$195.90
Purchase #6	$71.82	9.659%	$78.7571	$78.76	$78.75	$78.80
Purchase #7	$28.94	9.186%	$31.5984	$31.60	$31.60	$31.60
7 purchase totals =	$806.31		$886.4679	$886.47	$886.45	$886.60