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	$38.61	7.596%	$41.5428	$41.54	$41.55	$41.50
Purchase #2	$146.83	5.353%	$154.6898	$154.69	$154.70	$154.70
Purchase #3	$247.45	4.676%	$259.0208	$259.02	$259.00	$259.00
Purchase #4	$185.42	4.362%	$193.508	$193.51	$193.50	$193.50
Purchase #5	$211.41	3.416%	$218.6318	$218.63	$218.65	$218.60
Purchase #6	$123.41	12.260%	$138.5401	$138.54	$138.55	$138.50
Purchase #7	$73.57	6.690%	$78.4918	$78.49	$78.50	$78.50
7 purchase totals =	$1,026.70		$1,084.4251	$1,084.42	$1,084.45	$1,084.30