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	$54.27	5.874%	$57.4578	$57.46	$57.45	$57.50
Purchase #2	$59.87	13.110%	$67.719	$67.72	$67.70	$67.70
Purchase #3	$151.38	10.321%	$167.0039	$167.00	$167.00	$167.00
Purchase #4	$90.82	6.301%	$96.5426	$96.54	$96.55	$96.50
Purchase #5	$57.40	7.154%	$61.5064	$61.51	$61.50	$61.50
Purchase #6	$115.72	3.315%	$119.5561	$119.56	$119.55	$119.60
Purchase #7	$59.32	7.615%	$63.8372	$63.84	$63.85	$63.80
7 purchase totals =	$588.78		$633.6230	$633.63	$633.60	$633.60