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	$71.69	3.123%	$73.9289	$73.93	$73.95	$73.90
Purchase #2	$144.80	5.418%	$152.6453	$152.65	$152.65	$152.60
Purchase #3	$177.77	3.694%	$184.3368	$184.34	$184.35	$184.30
Purchase #4	$166.90	7.205%	$178.9251	$178.93	$178.95	$178.90
Purchase #5	$157.51	13.308%	$178.4714	$178.47	$178.45	$178.50
Purchase #6	$109.97	9.213%	$120.1015	$120.10	$120.10	$120.10
Purchase #7	$126.86	3.322%	$131.0743	$131.07	$131.05	$131.10
7 purchase totals =	$955.50		$1,019.4833	$1,019.49	$1,019.50	$1,019.40