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	$109.81	12.447%	$123.4781	$123.48	$123.50	$123.50
Purchase #2	$13.34	11.769%	$14.91	$14.91	$14.90	$14.90
Purchase #3	$59.42	13.285%	$67.3139	$67.31	$67.30	$67.30
Purchase #4	$54.76	9.112%	$59.7497	$59.75	$59.75	$59.70
Purchase #5	$102.72	10.817%	$113.8312	$113.83	$113.85	$113.80
Purchase #6	$158.44	12.711%	$178.5793	$178.58	$178.60	$178.60
Purchase #7	$14.42	7.371%	$15.4829	$15.48	$15.50	$15.50
7 purchase totals =	$512.91		$573.3451	$573.34	$573.40	$573.30