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	$157.46	3.248%	$162.5743	$162.57	$162.55	$162.60
Purchase #2	$227.69	5.257%	$239.6597	$239.66	$239.65	$239.70
Purchase #3	$161.90	13.251%	$183.3534	$183.35	$183.35	$183.40
Purchase #4	$79.47	13.442%	$90.1524	$90.15	$90.15	$90.20
Purchase #5	$186.62	10.141%	$205.5451	$205.55	$205.55	$205.50
Purchase #6	$49.90	6.241%	$53.0143	$53.01	$53.00	$53.00
Purchase #7	$196.78	7.846%	$212.2194	$212.22	$212.20	$212.20
7 purchase totals =	$1,059.82		$1,146.5186	$1,146.51	$1,146.45	$1,146.60