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	$248.82	5.176%	$261.6989	$261.70	$261.70	$261.70
Purchase #2	$203.85	13.764%	$231.9079	$231.91	$231.90	$231.90
Purchase #3	$59.36	3.484%	$61.4281	$61.43	$61.45	$61.40
Purchase #4	$49.29	10.521%	$54.4758	$54.48	$54.50	$54.50
Purchase #5	$93.28	9.868%	$102.4849	$102.48	$102.50	$102.50
Purchase #6	$88.39	3.474%	$91.4607	$91.46	$91.45	$91.50
Purchase #7	$163.33	11.464%	$182.0542	$182.05	$182.05	$182.10
7 purchase totals =	$906.32		$985.5105	$985.51	$985.55	$985.60