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	$185.46	6.178%	$196.9177	$196.92	$196.90	$196.90
Purchase #2	$141.67	9.110%	$154.5761	$154.58	$154.60	$154.60
Purchase #3	$238.46	9.586%	$261.3188	$261.32	$261.30	$261.30
Purchase #4	$171.97	8.603%	$186.7646	$186.76	$186.75	$186.80
Purchase #5	$135.43	3.671%	$140.4016	$140.40	$140.40	$140.40
Purchase #6	$148.39	13.538%	$168.479	$168.48	$168.50	$168.50
Purchase #7	$43.57	10.212%	$48.0194	$48.02	$48.00	$48.00
7 purchase totals =	$1,064.95		$1,156.4772	$1,156.48	$1,156.45	$1,156.50