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	$110.61	7.687%	$119.1126	$119.11	$119.10	$119.10
Purchase #2	$154.35	9.828%	$169.5195	$169.52	$169.50	$169.50
Purchase #3	$121.72	8.170%	$131.6645	$131.66	$131.65	$131.70
Purchase #4	$188.97	4.219%	$196.9426	$196.94	$196.95	$196.90
Purchase #5	$152.71	3.672%	$158.3175	$158.32	$158.30	$158.30
Purchase #6	$91.61	9.228%	$100.0638	$100.06	$100.05	$100.10
Purchase #7	$10.89	9.500%	$11.9246	$11.92	$11.90	$11.90
7 purchase totals =	$830.86		$887.5451	$887.53	$887.45	$887.50