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	$201.63	10.336%	$222.4705	$222.47	$222.45	$222.50
Purchase #2	$123.66	13.627%	$140.5111	$140.51	$140.50	$140.50
Purchase #3	$85.56	4.314%	$89.2511	$89.25	$89.25	$89.30
Purchase #4	$215.68	9.361%	$235.8698	$235.87	$235.85	$235.90
Purchase #5	$43.63	6.444%	$46.4415	$46.44	$46.45	$46.40
Purchase #6	$203.36	9.301%	$222.2745	$222.27	$222.25	$222.30
Purchase #7	$78.36	9.480%	$85.7885	$85.79	$85.80	$85.80
7 purchase totals =	$951.88		$1,042.6070	$1,042.60	$1,042.55	$1,042.70