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	$160.40	4.718%	$167.9677	$167.97	$167.95	$168.00
Purchase #2	$40.51	9.569%	$44.3864	$44.39	$44.40	$44.40
Purchase #3	$86.47	3.431%	$89.4368	$89.44	$89.45	$89.40
Purchase #4	$244.33	10.821%	$270.7689	$270.77	$270.75	$270.80
Purchase #5	$153.46	10.801%	$170.0352	$170.04	$170.05	$170.00
Purchase #6	$73.48	12.333%	$82.5423	$82.54	$82.55	$82.50
Purchase #7	$203.83	11.326%	$226.9158	$226.92	$226.90	$226.90
7 purchase totals =	$962.48		$1,052.0531	$1,052.07	$1,052.05	$1,052.00