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	$77.63	4.706%	$81.2833	$81.28	$81.30	$81.30
Purchase #2	$41.64	4.788%	$43.6337	$43.63	$43.65	$43.60
Purchase #3	$165.48	3.177%	$170.7373	$170.74	$170.75	$170.70
Purchase #4	$171.27	3.739%	$177.6738	$177.67	$177.65	$177.70
Purchase #5	$189.39	3.686%	$196.3709	$196.37	$196.35	$196.40
Purchase #6	$197.44	12.654%	$222.4241	$222.42	$222.40	$222.40
Purchase #7	$230.63	10.713%	$255.3374	$255.34	$255.35	$255.30
7 purchase totals =	$1,073.48		$1,147.4605	$1,147.45	$1,147.45	$1,147.40