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	$155.40	4.497%	$162.3883	$162.39	$162.40	$162.40
Purchase #2	$183.56	3.716%	$190.3811	$190.38	$190.40	$190.40
Purchase #3	$218.98	12.151%	$245.5883	$245.59	$245.60	$245.60
Purchase #4	$68.96	9.761%	$75.6912	$75.69	$75.70	$75.70
Purchase #5	$246.29	6.159%	$261.459	$261.46	$261.45	$261.50
Purchase #6	$107.86	3.197%	$111.3083	$111.31	$111.30	$111.30
Purchase #7	$30.58	9.398%	$33.4539	$33.45	$33.45	$33.50
7 purchase totals =	$1,011.63		$1,080.2701	$1,080.27	$1,080.30	$1,080.40