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	$164.76	4.226%	$171.7228	$171.72	$171.70	$171.70
Purchase #2	$29.81	6.686%	$31.8031	$31.80	$31.80	$31.80
Purchase #3	$121.40	9.369%	$132.774	$132.77	$132.75	$132.80
Purchase #4	$198.27	12.508%	$223.0696	$223.07	$223.05	$223.10
Purchase #5	$94.37	9.667%	$103.4927	$103.49	$103.50	$103.50
Purchase #6	$209.43	3.327%	$216.3977	$216.40	$216.40	$216.40
Purchase #7	$234.49	12.490%	$263.7778	$263.78	$263.80	$263.80
7 purchase totals =	$1,052.53		$1,143.0377	$1,143.03	$1,143.00	$1,143.10