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	$249.25	7.435%	$267.7817	$267.78	$267.80	$267.80
Purchase #2	$39.29	7.538%	$42.2517	$42.25	$42.25	$42.30
Purchase #3	$9.89	6.310%	$10.5141	$10.51	$10.50	$10.50
Purchase #4	$100.62	3.828%	$104.4717	$104.47	$104.45	$104.50
Purchase #5	$70.40	8.730%	$76.5459	$76.55	$76.55	$76.50
Purchase #6	$229.61	12.765%	$258.9197	$258.92	$258.90	$258.90
Purchase #7	$116.53	8.855%	$126.8487	$126.85	$126.85	$126.80
7 purchase totals =	$815.59		$887.3335	$887.33	$887.30	$887.30