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	$117.73	10.438%	$130.0187	$130.02	$130.00	$130.00
Purchase #2	$60.76	11.602%	$67.8094	$67.81	$67.80	$67.80
Purchase #3	$25.88	11.378%	$28.8246	$28.82	$28.80	$28.80
Purchase #4	$6.62	13.732%	$7.5291	$7.53	$7.55	$7.50
Purchase #5	$141.66	13.222%	$160.3903	$160.39	$160.40	$160.40
Purchase #6	$158.51	3.668%	$164.3241	$164.32	$164.30	$164.30
Purchase #7	$228.39	13.355%	$258.8915	$258.89	$258.90	$258.90
7 purchase totals =	$739.55		$817.7877	$817.78	$817.75	$817.70