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	$151.25	3.745%	$156.9143	$156.91	$156.90	$156.90
Purchase #2	$164.76	5.855%	$174.4067	$174.41	$174.40	$174.40
Purchase #3	$59.49	3.388%	$61.5055	$61.51	$61.50	$61.50
Purchase #4	$181.84	9.778%	$199.6203	$199.62	$199.60	$199.60
Purchase #5	$244.54	5.537%	$258.0802	$258.08	$258.10	$258.10
Purchase #6	$230.58	4.270%	$240.4258	$240.43	$240.45	$240.40
Purchase #7	$133.56	13.638%	$151.7749	$151.77	$151.75	$151.80
7 purchase totals =	$1,166.02		$1,242.7277	$1,242.73	$1,242.70	$1,242.70