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	$202.41	10.527%	$223.7177	$223.72	$223.70	$223.70
Purchase #2	$73.30	12.466%	$82.4376	$82.44	$82.45	$82.40
Purchase #3	$234.39	3.156%	$241.7873	$241.79	$241.80	$241.80
Purchase #4	$103.42	13.270%	$117.1438	$117.14	$117.15	$117.10
Purchase #5	$55.33	11.862%	$61.8932	$61.89	$61.90	$61.90
Purchase #6	$150.31	4.853%	$157.6045	$157.60	$157.60	$157.60
Purchase #7	$93.81	3.546%	$97.1365	$97.14	$97.15	$97.10
7 purchase totals =	$912.97		$981.7206	$981.72	$981.75	$981.60