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	$213.31	10.127%	$234.9119	$234.91	$234.90	$234.90
Purchase #2	$90.32	4.785%	$94.6418	$94.64	$94.65	$94.60
Purchase #3	$56.76	3.503%	$58.7483	$58.75	$58.75	$58.70
Purchase #4	$77.35	6.665%	$82.5054	$82.51	$82.50	$82.50
Purchase #5	$179.37	10.489%	$198.1841	$198.18	$198.20	$198.20
Purchase #6	$237.86	6.549%	$253.4375	$253.44	$253.45	$253.40
Purchase #7	$74.57	4.687%	$78.0651	$78.07	$78.05	$78.10
7 purchase totals =	$929.54		$1,000.4941	$1,000.50	$1,000.50	$1,000.40