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	$12.55	12.821%	$14.159	$14.16	$14.15	$14.20
Purchase #2	$224.31	10.827%	$248.596	$248.60	$248.60	$248.60
Purchase #3	$137.44	6.617%	$146.5344	$146.53	$146.55	$146.50
Purchase #4	$210.70	10.801%	$233.4577	$233.46	$233.45	$233.50
Purchase #5	$53.39	7.703%	$57.5026	$57.50	$57.50	$57.50
Purchase #6	$62.82	7.651%	$67.6264	$67.63	$67.65	$67.60
Purchase #7	$194.60	8.629%	$211.392	$211.39	$211.40	$211.40
7 purchase totals =	$895.81		$979.2681	$979.27	$979.30	$979.30