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	$248.46	11.837%	$277.8702	$277.87	$277.85	$277.90
Purchase #2	$140.59	7.172%	$150.6731	$150.67	$150.65	$150.70
Purchase #3	$229.90	3.668%	$238.3327	$238.33	$238.35	$238.30
Purchase #4	$75.88	8.177%	$82.0847	$82.08	$82.10	$82.10
Purchase #5	$78.39	9.511%	$85.8457	$85.85	$85.85	$85.80
Purchase #6	$164.92	5.305%	$173.669	$173.67	$173.65	$173.70
Purchase #7	$98.56	4.128%	$102.6286	$102.63	$102.65	$102.60
7 purchase totals =	$1,036.70		$1,111.1040	$1,111.10	$1,111.10	$1,111.10