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	$177.92	4.469%	$185.8712	$185.87	$185.85	$185.90
Purchase #2	$54.52	9.837%	$59.8831	$59.88	$59.90	$59.90
Purchase #3	$239.86	11.164%	$266.638	$266.64	$266.65	$266.60
Purchase #4	$113.44	8.477%	$123.0563	$123.06	$123.05	$123.10
Purchase #5	$160.60	5.304%	$169.1182	$169.12	$169.10	$169.10
Purchase #6	$46.48	5.497%	$49.035	$49.04	$49.05	$49.00
Purchase #7	$77.43	7.870%	$83.5237	$83.52	$83.50	$83.50
7 purchase totals =	$870.25		$937.1255	$937.13	$937.10	$937.10