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	$97.88	6.121%	$103.8712	$103.87	$103.85	$103.90
Purchase #2	$189.39	4.193%	$197.3311	$197.33	$197.35	$197.30
Purchase #3	$117.41	11.306%	$130.6844	$130.68	$130.70	$130.70
Purchase #4	$227.49	7.215%	$243.9034	$243.90	$243.90	$243.90
Purchase #5	$114.87	4.371%	$119.891	$119.89	$119.90	$119.90
Purchase #6	$22.25	7.236%	$23.86	$23.86	$23.85	$23.90
Purchase #7	$235.88	12.716%	$265.8745	$265.87	$265.85	$265.90
7 purchase totals =	$1,005.17		$1,085.4156	$1,085.40	$1,085.40	$1,085.50