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	$145.70	13.682%	$165.6347	$165.63	$165.65	$165.60
Purchase #2	$117.49	11.673%	$131.2046	$131.20	$131.20	$131.20
Purchase #3	$212.76	6.642%	$226.8915	$226.89	$226.90	$226.90
Purchase #4	$83.79	8.456%	$90.8753	$90.88	$90.90	$90.90
Purchase #5	$81.81	12.382%	$91.9397	$91.94	$91.95	$91.90
Purchase #6	$160.73	9.723%	$176.3578	$176.36	$176.35	$176.40
Purchase #7	$56.33	10.277%	$62.119	$62.12	$62.10	$62.10
7 purchase totals =	$858.61		$945.0226	$945.02	$945.05	$945.00