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	$43.71	11.201%	$48.606	$48.61	$48.60	$48.60
Purchase #2	$220.63	7.180%	$236.4712	$236.47	$236.45	$236.50
Purchase #3	$93.64	13.102%	$105.9087	$105.91	$105.90	$105.90
Purchase #4	$78.93	9.860%	$86.7125	$86.71	$86.70	$86.70
Purchase #5	$133.32	13.154%	$150.8569	$150.86	$150.85	$150.90
Purchase #6	$174.29	9.501%	$190.8493	$190.85	$190.85	$190.80
Purchase #7	$242.56	7.635%	$261.0795	$261.08	$261.10	$261.10
7 purchase totals =	$987.08		$1,080.4841	$1,080.49	$1,080.45	$1,080.50