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	$180.34	4.651%	$188.7276	$188.73	$188.75	$188.70
Purchase #2	$86.82	6.672%	$92.6126	$92.61	$92.60	$92.60
Purchase #3	$53.43	6.155%	$56.7186	$56.72	$56.70	$56.70
Purchase #4	$246.43	12.193%	$276.4772	$276.48	$276.50	$276.50
Purchase #5	$231.76	11.712%	$258.9037	$258.90	$258.90	$258.90
Purchase #6	$174.31	9.322%	$190.5592	$190.56	$190.55	$190.60
Purchase #7	$177.38	4.696%	$185.7098	$185.71	$185.70	$185.70
7 purchase totals =	$1,150.47		$1,249.7087	$1,249.71	$1,249.70	$1,249.70