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	$167.85	5.363%	$176.8518	$176.85	$176.85	$176.90
Purchase #2	$77.95	6.323%	$82.8788	$82.88	$82.90	$82.90
Purchase #3	$18.35	4.303%	$19.1396	$19.14	$19.15	$19.10
Purchase #4	$94.40	11.747%	$105.4892	$105.49	$105.50	$105.50
Purchase #5	$90.96	10.601%	$100.6027	$100.60	$100.60	$100.60
Purchase #6	$206.79	4.622%	$216.3478	$216.35	$216.35	$216.30
Purchase #7	$189.32	4.445%	$197.7353	$197.74	$197.75	$197.70
7 purchase totals =	$845.62		$899.0452	$899.05	$899.10	$899.00