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	$199.28	9.692%	$218.5942	$218.59	$218.60	$218.60
Purchase #2	$28.33	10.728%	$31.3692	$31.37	$31.35	$31.40
Purchase #3	$6.55	11.557%	$7.307	$7.31	$7.30	$7.30
Purchase #4	$138.64	13.326%	$157.1152	$157.12	$157.10	$157.10
Purchase #5	$132.81	4.287%	$138.5036	$138.50	$138.50	$138.50
Purchase #6	$72.55	13.519%	$82.358	$82.36	$82.35	$82.40
Purchase #7	$145.29	4.723%	$152.152	$152.15	$152.15	$152.20
7 purchase totals =	$723.45		$787.3992	$787.40	$787.35	$787.50