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	$62.87	7.814%	$67.7827	$67.78	$67.80	$67.80
Purchase #2	$200.99	13.713%	$228.5518	$228.55	$228.55	$228.60
Purchase #3	$164.51	4.510%	$171.9294	$171.93	$171.95	$171.90
Purchase #4	$232.34	11.392%	$258.8082	$258.81	$258.80	$258.80
Purchase #5	$158.32	12.820%	$178.6166	$178.62	$178.60	$178.60
Purchase #6	$224.81	6.123%	$238.5751	$238.58	$238.60	$238.60
Purchase #7	$211.58	4.614%	$221.3423	$221.34	$221.35	$221.30
7 purchase totals =	$1,255.42		$1,365.6061	$1,365.61	$1,365.65	$1,365.60