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	$55.95	11.148%	$62.1873	$62.19	$62.20	$62.20
Purchase #2	$122.85	4.144%	$127.9409	$127.94	$127.95	$127.90
Purchase #3	$230.91	11.253%	$256.8943	$256.89	$256.90	$256.90
Purchase #4	$187.75	4.287%	$195.7988	$195.80	$195.80	$195.80
Purchase #5	$148.47	10.831%	$164.5508	$164.55	$164.55	$164.60
Purchase #6	$183.60	3.152%	$189.3871	$189.39	$189.40	$189.40
Purchase #7	$42.83	3.620%	$44.3804	$44.38	$44.40	$44.40
7 purchase totals =	$972.36		$1,041.1396	$1,041.14	$1,041.20	$1,041.20