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	$137.57	13.208%	$155.7402	$155.74	$155.75	$155.70
Purchase #2	$126.48	11.624%	$141.182	$141.18	$141.20	$141.20
Purchase #3	$149.91	7.338%	$160.9104	$160.91	$160.90	$160.90
Purchase #4	$55.38	8.757%	$60.2296	$60.23	$60.25	$60.20
Purchase #5	$177.37	7.784%	$191.1765	$191.18	$191.20	$191.20
Purchase #6	$150.64	9.697%	$165.2476	$165.25	$165.25	$165.20
Purchase #7	$127.77	11.463%	$142.4163	$142.42	$142.40	$142.40
7 purchase totals =	$925.12		$1,016.9026	$1,016.91	$1,016.95	$1,016.80