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	$99.58	6.126%	$105.6803	$105.68	$105.70	$105.70
Purchase #2	$100.40	3.323%	$103.7363	$103.74	$103.75	$103.70
Purchase #3	$22.46	6.138%	$23.8386	$23.84	$23.85	$23.80
Purchase #4	$98.53	10.523%	$108.8983	$108.90	$108.90	$108.90
Purchase #5	$186.43	5.607%	$196.8831	$196.88	$196.90	$196.90
Purchase #6	$61.51	4.743%	$64.4274	$64.43	$64.45	$64.40
Purchase #7	$156.39	7.292%	$167.794	$167.79	$167.80	$167.80
7 purchase totals =	$725.30		$771.2580	$771.26	$771.35	$771.20