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	$96.75	13.211%	$109.5316	$109.53	$109.55	$109.50
Purchase #2	$114.29	4.586%	$119.5313	$119.53	$119.55	$119.50
Purchase #3	$103.32	9.808%	$113.4536	$113.45	$113.45	$113.50
Purchase #4	$176.35	11.235%	$196.1629	$196.16	$196.15	$196.20
Purchase #5	$99.48	13.583%	$112.9924	$112.99	$113.00	$113.00
Purchase #6	$227.44	9.852%	$249.8474	$249.85	$249.85	$249.80
Purchase #7	$162.48	7.736%	$175.0495	$175.05	$175.05	$175.00
7 purchase totals =	$980.11		$1,076.5687	$1,076.56	$1,076.60	$1,076.50