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	$117.39	4.786%	$123.0083	$123.01	$123.00	$123.00
Purchase #2	$31.97	3.690%	$33.1497	$33.15	$33.15	$33.10
Purchase #3	$182.84	6.594%	$194.8965	$194.90	$194.90	$194.90
Purchase #4	$160.93	4.788%	$168.6353	$168.64	$168.65	$168.60
Purchase #5	$98.56	7.135%	$105.5923	$105.59	$105.60	$105.60
Purchase #6	$218.74	7.250%	$234.5987	$234.60	$234.60	$234.60
Purchase #7	$201.98	7.651%	$217.4335	$217.43	$217.45	$217.40
7 purchase totals =	$1,012.41		$1,077.3143	$1,077.32	$1,077.35	$1,077.20