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	$59.25	13.641%	$67.3323	$67.33	$67.35	$67.30
Purchase #2	$192.93	12.615%	$217.2681	$217.27	$217.25	$217.30
Purchase #3	$244.81	8.817%	$266.3949	$266.39	$266.40	$266.40
Purchase #4	$47.27	13.374%	$53.5919	$53.59	$53.60	$53.60
Purchase #5	$77.45	10.874%	$85.8719	$85.87	$85.85	$85.90
Purchase #6	$213.54	9.109%	$232.9914	$232.99	$233.00	$233.00
Purchase #7	$55.70	3.740%	$57.7832	$57.78	$57.80	$57.80
7 purchase totals =	$890.95		$981.2337	$981.22	$981.25	$981.30