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	$92.89	12.555%	$104.5523	$104.55	$104.55	$104.60
Purchase #2	$225.97	10.731%	$250.2188	$250.22	$250.20	$250.20
Purchase #3	$186.70	4.167%	$194.4798	$194.48	$194.50	$194.50
Purchase #4	$121.90	6.691%	$130.0563	$130.06	$130.05	$130.10
Purchase #5	$116.94	3.810%	$121.3954	$121.40	$121.40	$121.40
Purchase #6	$176.43	11.360%	$196.4724	$196.47	$196.45	$196.50
Purchase #7	$40.76	9.483%	$44.6253	$44.63	$44.65	$44.60
7 purchase totals =	$961.59		$1,041.8003	$1,041.81	$1,041.80	$1,041.90