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	$98.82	10.835%	$109.5271	$109.53	$109.55	$109.50
Purchase #2	$76.66	12.535%	$86.2693	$86.27	$86.25	$86.30
Purchase #3	$90.45	8.610%	$98.2377	$98.24	$98.25	$98.20
Purchase #4	$151.45	7.213%	$162.3741	$162.37	$162.35	$162.40
Purchase #5	$124.25	8.729%	$135.0958	$135.10	$135.10	$135.10
Purchase #6	$72.46	8.781%	$78.8227	$78.82	$78.80	$78.80
Purchase #7	$33.92	11.193%	$37.7167	$37.72	$37.70	$37.70
7 purchase totals =	$648.01		$708.0434	$708.05	$708.00	$708.00