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	$139.54	3.667%	$144.6569	$144.66	$144.65	$144.70
Purchase #2	$184.42	5.269%	$194.1371	$194.14	$194.15	$194.10
Purchase #3	$63.50	11.748%	$70.96	$70.96	$70.95	$71.00
Purchase #4	$235.35	13.607%	$267.3741	$267.37	$267.35	$267.40
Purchase #5	$77.35	5.499%	$81.6035	$81.60	$81.60	$81.60
Purchase #6	$219.96	10.326%	$242.6731	$242.67	$242.65	$242.70
Purchase #7	$89.26	11.483%	$99.5097	$99.51	$99.50	$99.50
7 purchase totals =	$1,009.38		$1,100.9144	$1,100.91	$1,100.85	$1,101.00