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	$80.49	13.698%	$91.5155	$91.52	$91.50	$91.50
Purchase #2	$242.46	3.482%	$250.9025	$250.90	$250.90	$250.90
Purchase #3	$178.80	6.417%	$190.2736	$190.27	$190.25	$190.30
Purchase #4	$167.33	6.536%	$178.2667	$178.27	$178.25	$178.30
Purchase #5	$238.52	13.477%	$270.6653	$270.67	$270.65	$270.70
Purchase #6	$12.55	6.236%	$13.3326	$13.33	$13.35	$13.30
Purchase #7	$158.77	3.266%	$163.9554	$163.96	$163.95	$164.00
7 purchase totals =	$1,078.92		$1,158.9116	$1,158.92	$1,158.85	$1,159.00