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	$129.50	7.796%	$139.5958	$139.60	$139.60	$139.60
Purchase #2	$125.66	10.823%	$139.2602	$139.26	$139.25	$139.30
Purchase #3	$191.71	4.305%	$199.9631	$199.96	$199.95	$200.00
Purchase #4	$75.82	9.493%	$83.0176	$83.02	$83.00	$83.00
Purchase #5	$172.61	7.570%	$185.6766	$185.68	$185.70	$185.70
Purchase #6	$209.56	11.533%	$233.7286	$233.73	$233.75	$233.70
Purchase #7	$37.99	12.414%	$42.7061	$42.71	$42.70	$42.70
7 purchase totals =	$942.85		$1,023.9480	$1,023.96	$1,023.95	$1,024.00