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	$104.58	8.782%	$113.7642	$113.76	$113.75	$113.80
Purchase #2	$103.60	7.426%	$111.2933	$111.29	$111.30	$111.30
Purchase #3	$190.79	9.839%	$209.5618	$209.56	$209.55	$209.60
Purchase #4	$181.85	3.309%	$187.8674	$187.87	$187.85	$187.90
Purchase #5	$140.31	10.612%	$155.1997	$155.20	$155.20	$155.20
Purchase #6	$140.33	11.772%	$156.8496	$156.85	$156.85	$156.80
Purchase #7	$42.48	13.501%	$48.2152	$48.22	$48.20	$48.20
7 purchase totals =	$903.94		$982.7512	$982.75	$982.70	$982.80