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	$193.42	8.497%	$209.8549	$209.85	$209.85	$209.90
Purchase #2	$80.39	12.325%	$90.2981	$90.30	$90.30	$90.30
Purchase #3	$194.95	13.170%	$220.6249	$220.62	$220.60	$220.60
Purchase #4	$116.28	10.746%	$128.7754	$128.78	$128.80	$128.80
Purchase #5	$198.32	8.845%	$215.8614	$215.86	$215.85	$215.90
Purchase #6	$140.28	7.443%	$150.721	$150.72	$150.70	$150.70
Purchase #7	$162.25	7.588%	$174.5615	$174.56	$174.55	$174.60
7 purchase totals =	$1,085.89		$1,190.6972	$1,190.69	$1,190.65	$1,190.80