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	$118.28	11.698%	$132.1164	$132.12	$132.10	$132.10
Purchase #2	$137.93	12.503%	$155.1754	$155.18	$155.20	$155.20
Purchase #3	$185.33	7.284%	$198.8294	$198.83	$198.85	$198.80
Purchase #4	$141.41	6.745%	$150.9481	$150.95	$150.95	$150.90
Purchase #5	$78.86	4.692%	$82.5601	$82.56	$82.55	$82.60
Purchase #6	$77.79	12.845%	$87.7821	$87.78	$87.80	$87.80
Purchase #7	$198.88	3.458%	$205.7573	$205.76	$205.75	$205.80
7 purchase totals =	$938.48		$1,013.1688	$1,013.18	$1,013.20	$1,013.20