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	$237.32	3.438%	$245.4791	$245.48	$245.50	$245.50
Purchase #2	$60.62	7.813%	$65.3562	$65.36	$65.35	$65.40
Purchase #3	$46.64	12.447%	$52.4453	$52.45	$52.45	$52.40
Purchase #4	$165.31	13.569%	$187.7409	$187.74	$187.75	$187.70
Purchase #5	$75.75	6.212%	$80.4556	$80.46	$80.45	$80.50
Purchase #6	$90.75	4.172%	$94.5361	$94.54	$94.55	$94.50
Purchase #7	$116.89	9.316%	$127.7795	$127.78	$127.80	$127.80
7 purchase totals =	$793.28		$853.7927	$853.81	$853.85	$853.80