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	$128.34	11.306%	$142.8501	$142.85	$142.85	$142.90
Purchase #2	$77.33	4.324%	$80.6737	$80.67	$80.65	$80.70
Purchase #3	$164.65	12.428%	$185.1127	$185.11	$185.10	$185.10
Purchase #4	$138.30	8.117%	$149.5258	$149.53	$149.55	$149.50
Purchase #5	$216.63	9.236%	$236.6379	$236.64	$236.65	$236.60
Purchase #6	$103.54	5.357%	$109.0866	$109.09	$109.10	$109.10
Purchase #7	$163.95	5.447%	$172.8804	$172.88	$172.90	$172.90
7 purchase totals =	$992.74		$1,076.7672	$1,076.77	$1,076.80	$1,076.80