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	$184.53	3.155%	$190.3519	$190.35	$190.35	$190.40
Purchase #2	$227.92	7.626%	$245.3012	$245.30	$245.30	$245.30
Purchase #3	$57.40	4.393%	$59.9216	$59.92	$59.90	$59.90
Purchase #4	$147.31	4.761%	$154.3234	$154.32	$154.30	$154.30
Purchase #5	$171.72	3.211%	$177.2339	$177.23	$177.25	$177.20
Purchase #6	$113.62	4.232%	$118.4284	$118.43	$118.45	$118.40
Purchase #7	$78.30	3.371%	$80.9395	$80.94	$80.95	$80.90
7 purchase totals =	$980.80		$1,026.4999	$1,026.49	$1,026.50	$1,026.40