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	$207.98	3.506%	$215.2718	$215.27	$215.25	$215.30
Purchase #2	$51.37	8.740%	$55.8597	$55.86	$55.85	$55.90
Purchase #3	$168.41	6.460%	$179.2893	$179.29	$179.30	$179.30
Purchase #4	$48.82	6.122%	$51.8088	$51.81	$51.80	$51.80
Purchase #5	$151.93	13.626%	$172.632	$172.63	$172.65	$172.60
Purchase #6	$54.58	3.838%	$56.6748	$56.67	$56.65	$56.70
Purchase #7	$111.92	11.162%	$124.4125	$124.41	$124.40	$124.40
7 purchase totals =	$795.01		$855.9489	$855.94	$855.90	$856.00