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	$52.66	4.401%	$54.9776	$54.98	$55.00	$55.00
Purchase #2	$191.81	13.326%	$217.3706	$217.37	$217.35	$217.40
Purchase #3	$157.36	10.734%	$174.251	$174.25	$174.25	$174.30
Purchase #4	$181.48	8.504%	$196.9131	$196.91	$196.90	$196.90
Purchase #5	$86.48	9.259%	$94.4872	$94.49	$94.50	$94.50
Purchase #6	$144.34	11.190%	$160.4916	$160.49	$160.50	$160.50
Purchase #7	$54.50	3.260%	$56.2767	$56.28	$56.30	$56.30
7 purchase totals =	$868.63		$954.7678	$954.77	$954.80	$954.90