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	$157.63	7.541%	$169.5169	$169.52	$169.50	$169.50
Purchase #2	$80.43	12.416%	$90.4162	$90.42	$90.40	$90.40
Purchase #3	$164.57	6.851%	$175.8447	$175.84	$175.85	$175.80
Purchase #4	$10.81	8.469%	$11.7255	$11.73	$11.75	$11.70
Purchase #5	$143.45	13.223%	$162.4184	$162.42	$162.40	$162.40
Purchase #6	$53.86	7.538%	$57.92	$57.92	$57.90	$57.90
Purchase #7	$17.34	5.730%	$18.3336	$18.33	$18.35	$18.30
7 purchase totals =	$628.09		$686.1753	$686.18	$686.15	$686.00