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	$224.55	8.498%	$243.6323	$243.63	$243.65	$243.60
Purchase #2	$243.72	9.681%	$267.3145	$267.31	$267.30	$267.30
Purchase #3	$176.81	9.831%	$194.1922	$194.19	$194.20	$194.20
Purchase #4	$99.43	5.382%	$104.7813	$104.78	$104.80	$104.80
Purchase #5	$83.74	3.458%	$86.6357	$86.64	$86.65	$86.60
Purchase #6	$37.64	12.781%	$42.4508	$42.45	$42.45	$42.50
Purchase #7	$58.83	7.744%	$63.3858	$63.39	$63.40	$63.40
7 purchase totals =	$924.72		$1,002.3926	$1,002.39	$1,002.45	$1,002.40