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	$218.31	11.831%	$244.1383	$244.14	$244.15	$244.10
Purchase #2	$115.71	7.183%	$124.0214	$124.02	$124.00	$124.00
Purchase #3	$180.74	3.500%	$187.0659	$187.07	$187.05	$187.10
Purchase #4	$45.58	13.445%	$51.7082	$51.71	$51.70	$51.70
Purchase #5	$150.81	11.304%	$167.8576	$167.86	$167.85	$167.90
Purchase #6	$144.68	4.106%	$150.6206	$150.62	$150.60	$150.60
Purchase #7	$137.89	8.807%	$150.034	$150.03	$150.05	$150.00
7 purchase totals =	$993.72		$1,075.4460	$1,075.45	$1,075.40	$1,075.40