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	$125.76	4.333%	$131.2092	$131.21	$131.20	$131.20
Purchase #2	$143.73	9.350%	$157.1688	$157.17	$157.15	$157.20
Purchase #3	$166.69	11.239%	$185.4243	$185.42	$185.40	$185.40
Purchase #4	$200.39	6.200%	$212.8142	$212.81	$212.80	$212.80
Purchase #5	$174.76	9.430%	$191.2399	$191.24	$191.25	$191.20
Purchase #6	$167.94	7.460%	$180.4683	$180.47	$180.45	$180.50
Purchase #7	$171.76	10.782%	$190.2792	$190.28	$190.30	$190.30
7 purchase totals =	$1,151.03		$1,248.6039	$1,248.60	$1,248.55	$1,248.60