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	$53.94	5.759%	$57.0464	$57.05	$57.05	$57.00
Purchase #2	$127.98	11.451%	$142.635	$142.64	$142.65	$142.60
Purchase #3	$130.56	6.274%	$138.7513	$138.75	$138.75	$138.80
Purchase #4	$88.48	11.748%	$98.8746	$98.87	$98.85	$98.90
Purchase #5	$131.94	9.482%	$144.4506	$144.45	$144.45	$144.50
Purchase #6	$32.44	9.639%	$35.5669	$35.57	$35.55	$35.60
Purchase #7	$73.41	7.427%	$78.8622	$78.86	$78.85	$78.90
7 purchase totals =	$638.75		$696.1870	$696.19	$696.15	$696.30