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	$75.65	7.676%	$81.4569	$81.46	$81.45	$81.50
Purchase #2	$219.71	4.460%	$229.5091	$229.51	$229.50	$229.50
Purchase #3	$51.76	4.591%	$54.1363	$54.14	$54.15	$54.10
Purchase #4	$211.83	4.819%	$222.0381	$222.04	$222.05	$222.00
Purchase #5	$159.34	4.754%	$166.915	$166.92	$166.90	$166.90
Purchase #6	$143.65	13.327%	$162.7942	$162.79	$162.80	$162.80
Purchase #7	$177.33	7.605%	$190.8159	$190.82	$190.80	$190.80
7 purchase totals =	$1,039.27		$1,107.6655	$1,107.68	$1,107.65	$1,107.60