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	$87.71	4.362%	$91.5359	$91.54	$91.55	$91.50
Purchase #2	$180.65	8.792%	$196.5327	$196.53	$196.55	$196.50
Purchase #3	$143.84	4.713%	$150.6192	$150.62	$150.60	$150.60
Purchase #4	$213.81	6.800%	$228.3491	$228.35	$228.35	$228.30
Purchase #5	$246.45	8.146%	$266.5258	$266.53	$266.55	$266.50
Purchase #6	$224.46	8.518%	$243.5795	$243.58	$243.60	$243.60
Purchase #7	$72.40	10.218%	$79.7978	$79.80	$79.80	$79.80
7 purchase totals =	$1,169.32		$1,256.9400	$1,256.95	$1,257.00	$1,256.80