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	$215.54	12.517%	$242.5191	$242.52	$242.50	$242.50
Purchase #2	$172.65	7.192%	$185.067	$185.07	$185.05	$185.10
Purchase #3	$96.61	13.314%	$109.4727	$109.47	$109.45	$109.50
Purchase #4	$62.36	10.460%	$68.8829	$68.88	$68.90	$68.90
Purchase #5	$116.52	8.749%	$126.7143	$126.71	$126.70	$126.70
Purchase #6	$166.34	8.741%	$180.8798	$180.88	$180.90	$180.90
Purchase #7	$179.68	9.331%	$196.4459	$196.45	$196.45	$196.40
7 purchase totals =	$1,009.70		$1,109.9817	$1,109.98	$1,109.95	$1,110.00