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	$119.93	3.212%	$123.7822	$123.78	$123.80	$123.80
Purchase #2	$241.82	9.557%	$264.9307	$264.93	$264.95	$264.90
Purchase #3	$182.67	9.578%	$200.1661	$200.17	$200.15	$200.20
Purchase #4	$169.67	10.357%	$187.2427	$187.24	$187.25	$187.20
Purchase #5	$114.85	13.352%	$130.1848	$130.18	$130.20	$130.20
Purchase #6	$164.58	12.849%	$185.7269	$185.73	$185.75	$185.70
Purchase #7	$80.98	3.656%	$83.9406	$83.94	$83.95	$83.90
7 purchase totals =	$1,074.50		$1,175.9740	$1,175.97	$1,176.05	$1,175.90