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	$100.86	5.682%	$106.5909	$106.59	$106.60	$106.60
Purchase #2	$195.25	4.503%	$204.0421	$204.04	$204.05	$204.00
Purchase #3	$167.39	11.441%	$186.5411	$186.54	$186.55	$186.50
Purchase #4	$220.84	6.169%	$234.4636	$234.46	$234.45	$234.50
Purchase #5	$174.72	12.677%	$196.8693	$196.87	$196.85	$196.90
Purchase #6	$165.26	12.441%	$185.82	$185.82	$185.80	$185.80
Purchase #7	$23.80	7.859%	$25.6704	$25.67	$25.65	$25.70
7 purchase totals =	$1,048.12		$1,139.9974	$1,139.99	$1,139.95	$1,140.00