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	$63.50	10.467%	$70.1465	$70.15	$70.15	$70.10
Purchase #2	$153.50	11.450%	$171.0758	$171.08	$171.10	$171.10
Purchase #3	$89.73	3.587%	$92.9486	$92.95	$92.95	$92.90
Purchase #4	$191.45	4.679%	$200.4079	$200.41	$200.40	$200.40
Purchase #5	$225.69	9.233%	$246.528	$246.53	$246.55	$246.50
Purchase #6	$81.95	6.565%	$87.33	$87.33	$87.35	$87.30
Purchase #7	$190.34	4.629%	$199.1508	$199.15	$199.15	$199.20
7 purchase totals =	$996.16		$1,067.5876	$1,067.60	$1,067.65	$1,067.50