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	$165.59	5.735%	$175.0866	$175.09	$175.10	$175.10
Purchase #2	$148.52	8.111%	$160.5665	$160.57	$160.55	$160.60
Purchase #3	$99.89	4.641%	$104.5259	$104.53	$104.55	$104.50
Purchase #4	$5.47	5.803%	$5.7874	$5.79	$5.80	$5.80
Purchase #5	$92.75	5.739%	$98.0729	$98.07	$98.05	$98.10
Purchase #6	$52.55	13.182%	$59.4771	$59.48	$59.50	$59.50
Purchase #7	$168.60	5.188%	$177.347	$177.35	$177.35	$177.30
7 purchase totals =	$733.37		$780.8634	$780.88	$780.90	$780.90