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	$81.94	10.762%	$90.7584	$90.76	$90.75	$90.80
Purchase #2	$160.96	3.339%	$166.3345	$166.33	$166.35	$166.30
Purchase #3	$53.40	5.666%	$56.4256	$56.43	$56.45	$56.40
Purchase #4	$82.60	4.255%	$86.1146	$86.11	$86.10	$86.10
Purchase #5	$230.41	3.351%	$238.131	$238.13	$238.15	$238.10
Purchase #6	$67.78	5.647%	$71.6075	$71.61	$71.60	$71.60
Purchase #7	$143.50	10.507%	$158.5775	$158.58	$158.60	$158.60
7 purchase totals =	$820.59		$867.9491	$867.95	$868.00	$867.90