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	$136.34	5.704%	$144.1168	$144.12	$144.10	$144.10
Purchase #2	$113.89	13.486%	$129.2492	$129.25	$129.25	$129.20
Purchase #3	$221.40	6.256%	$235.2508	$235.25	$235.25	$235.30
Purchase #4	$9.82	4.236%	$10.236	$10.24	$10.25	$10.20
Purchase #5	$175.51	8.344%	$190.1546	$190.15	$190.15	$190.20
Purchase #6	$171.86	6.228%	$182.5634	$182.56	$182.55	$182.60
Purchase #7	$134.25	12.345%	$150.8232	$150.82	$150.80	$150.80
7 purchase totals =	$963.07		$1,042.3940	$1,042.39	$1,042.35	$1,042.40