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	$137.55	12.294%	$154.4604	$154.46	$154.45	$154.50
Purchase #2	$101.51	9.719%	$111.3758	$111.38	$111.40	$111.40
Purchase #3	$19.29	7.695%	$20.7744	$20.77	$20.75	$20.80
Purchase #4	$75.81	9.203%	$82.7868	$82.79	$82.80	$82.80
Purchase #5	$205.66	10.836%	$227.9453	$227.95	$227.95	$227.90
Purchase #6	$96.31	3.279%	$99.468	$99.47	$99.45	$99.50
Purchase #7	$233.96	5.217%	$246.1657	$246.17	$246.15	$246.20
7 purchase totals =	$870.09		$942.9764	$942.99	$942.95	$943.10