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	$26.61	10.525%	$29.4107	$29.41	$29.40	$29.40
Purchase #2	$154.64	6.538%	$164.7504	$164.75	$164.75	$164.80
Purchase #3	$85.65	5.653%	$90.4918	$90.49	$90.50	$90.50
Purchase #4	$187.63	8.519%	$203.6142	$203.61	$203.60	$203.60
Purchase #5	$175.32	12.240%	$196.7792	$196.78	$196.80	$196.80
Purchase #6	$190.55	9.806%	$209.2353	$209.24	$209.25	$209.20
Purchase #7	$247.77	6.661%	$264.274	$264.27	$264.25	$264.30
7 purchase totals =	$1,068.17		$1,158.5556	$1,158.55	$1,158.55	$1,158.60