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	$51.59	4.262%	$53.7888	$53.79	$53.80	$53.80
Purchase #2	$69.46	11.715%	$77.5972	$77.60	$77.60	$77.60
Purchase #3	$40.94	3.251%	$42.271	$42.27	$42.25	$42.30
Purchase #4	$127.63	9.748%	$140.0714	$140.07	$140.05	$140.10
Purchase #5	$83.54	12.648%	$94.1061	$94.11	$94.10	$94.10
Purchase #6	$87.47	13.342%	$99.1402	$99.14	$99.15	$99.10
Purchase #7	$92.73	5.794%	$98.1028	$98.10	$98.10	$98.10
7 purchase totals =	$553.36		$605.0775	$605.08	$605.05	$605.10