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	$116.55	12.832%	$131.5057	$131.51	$131.50	$131.50
Purchase #2	$90.31	4.192%	$94.0958	$94.10	$94.10	$94.10
Purchase #3	$115.51	7.596%	$124.2841	$124.28	$124.30	$124.30
Purchase #4	$73.51	12.700%	$82.8458	$82.85	$82.85	$82.80
Purchase #5	$146.57	13.860%	$166.8846	$166.88	$166.90	$166.90
Purchase #6	$190.78	13.327%	$216.2053	$216.21	$216.20	$216.20
Purchase #7	$189.98	12.652%	$214.0163	$214.02	$214.00	$214.00
7 purchase totals =	$923.21		$1,029.8376	$1,029.85	$1,029.85	$1,029.80