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	$61.99	12.864%	$69.9644	$69.96	$69.95	$70.00
Purchase #2	$131.76	4.189%	$137.2794	$137.28	$137.30	$137.30
Purchase #3	$220.34	4.359%	$229.9446	$229.94	$229.95	$229.90
Purchase #4	$142.86	5.634%	$150.9087	$150.91	$150.90	$150.90
Purchase #5	$220.81	8.174%	$238.859	$238.86	$238.85	$238.90
Purchase #6	$194.43	5.645%	$205.4056	$205.41	$205.40	$205.40
Purchase #7	$52.48	6.556%	$55.9206	$55.92	$55.90	$55.90
7 purchase totals =	$1,024.67		$1,088.2823	$1,088.28	$1,088.25	$1,088.30