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	$118.73	4.156%	$123.6644	$123.66	$123.65	$123.70
Purchase #2	$153.60	4.339%	$160.2647	$160.26	$160.25	$160.30
Purchase #3	$161.39	4.689%	$168.9576	$168.96	$168.95	$169.00
Purchase #4	$186.38	5.266%	$196.1948	$196.19	$196.20	$196.20
Purchase #5	$18.36	5.356%	$19.3434	$19.34	$19.35	$19.30
Purchase #6	$139.45	12.460%	$156.8255	$156.83	$156.85	$156.80
Purchase #7	$51.82	3.492%	$53.6296	$53.63	$53.65	$53.60
7 purchase totals =	$829.73		$878.8800	$878.87	$878.90	$878.90