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	$104.94	13.543%	$119.152	$119.15	$119.15	$119.20
Purchase #2	$56.64	10.396%	$62.5283	$62.53	$62.55	$62.50
Purchase #3	$180.88	6.117%	$191.9444	$191.94	$191.95	$191.90
Purchase #4	$165.26	9.442%	$180.8638	$180.86	$180.85	$180.90
Purchase #5	$35.75	12.190%	$40.1079	$40.11	$40.10	$40.10
Purchase #6	$142.62	12.240%	$160.0767	$160.08	$160.10	$160.10
Purchase #7	$172.33	4.208%	$179.5816	$179.58	$179.60	$179.60
7 purchase totals =	$858.42		$934.2547	$934.25	$934.30	$934.30