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	$72.83	13.114%	$82.3809	$82.38	$82.40	$82.40
Purchase #2	$67.28	9.701%	$73.8068	$73.81	$73.80	$73.80
Purchase #3	$50.51	6.545%	$53.8159	$53.82	$53.80	$53.80
Purchase #4	$141.53	7.579%	$152.2566	$152.26	$152.25	$152.30
Purchase #5	$82.82	4.819%	$86.8111	$86.81	$86.80	$86.80
Purchase #6	$182.76	12.571%	$205.7348	$205.73	$205.75	$205.70
Purchase #7	$191.43	7.178%	$205.1708	$205.17	$205.15	$205.20
7 purchase totals =	$789.16		$859.9769	$859.98	$859.95	$860.00