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	$231.35	9.609%	$253.5804	$253.58	$253.60	$253.60
Purchase #2	$61.25	3.610%	$63.4611	$63.46	$63.45	$63.50
Purchase #3	$98.92	10.579%	$109.3847	$109.38	$109.40	$109.40
Purchase #4	$134.44	13.728%	$152.8959	$152.90	$152.90	$152.90
Purchase #5	$34.87	13.378%	$39.5349	$39.53	$39.55	$39.50
Purchase #6	$184.33	13.701%	$209.5851	$209.59	$209.60	$209.60
Purchase #7	$201.63	5.868%	$213.4616	$213.46	$213.45	$213.50
7 purchase totals =	$946.79		$1,041.9037	$1,041.90	$1,041.95	$1,042.00