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	$53.65	5.477%	$56.5884	$56.59	$56.60	$56.60
Purchase #2	$84.81	3.776%	$88.0124	$88.01	$88.00	$88.00
Purchase #3	$71.37	8.205%	$77.2259	$77.23	$77.25	$77.20
Purchase #4	$142.51	8.438%	$154.535	$154.54	$154.55	$154.50
Purchase #5	$173.56	13.463%	$196.9264	$196.93	$196.95	$196.90
Purchase #6	$36.73	5.665%	$38.8108	$38.81	$38.80	$38.80
Purchase #7	$184.67	10.104%	$203.3291	$203.33	$203.35	$203.30
7 purchase totals =	$747.30		$815.4280	$815.44	$815.50	$815.30