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	$11.31	12.115%	$12.6802	$12.68	$12.70	$12.70
Purchase #2	$170.98	7.416%	$183.6599	$183.66	$183.65	$183.70
Purchase #3	$68.34	7.259%	$73.3008	$73.30	$73.30	$73.30
Purchase #4	$17.95	9.436%	$19.6438	$19.64	$19.65	$19.60
Purchase #5	$81.81	10.654%	$90.526	$90.53	$90.55	$90.50
Purchase #6	$69.35	3.206%	$71.5734	$71.57	$71.55	$71.60
Purchase #7	$187.75	4.848%	$196.8521	$196.85	$196.85	$196.90
7 purchase totals =	$607.49		$648.2362	$648.23	$648.25	$648.30