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	$185.70	3.297%	$191.8225	$191.82	$191.80	$191.80
Purchase #2	$231.53	12.148%	$259.6563	$259.66	$259.65	$259.70
Purchase #3	$204.76	3.836%	$212.6146	$212.61	$212.60	$212.60
Purchase #4	$45.44	3.287%	$46.9336	$46.93	$46.95	$46.90
Purchase #5	$104.42	6.539%	$111.248	$111.25	$111.25	$111.20
Purchase #6	$10.33	12.616%	$11.6332	$11.63	$11.65	$11.60
Purchase #7	$12.38	9.391%	$13.5426	$13.54	$13.55	$13.50
7 purchase totals =	$794.56		$847.4508	$847.44	$847.45	$847.30