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	$48.64	11.704%	$54.3328	$54.33	$54.35	$54.30
Purchase #2	$220.51	9.578%	$241.6304	$241.63	$241.65	$241.60
Purchase #3	$80.59	5.839%	$85.2957	$85.30	$85.30	$85.30
Purchase #4	$108.31	9.420%	$118.5128	$118.51	$118.50	$118.50
Purchase #5	$118.39	8.527%	$128.4851	$128.49	$128.50	$128.50
Purchase #6	$189.31	12.173%	$212.3547	$212.35	$212.35	$212.40
Purchase #7	$198.80	5.274%	$209.2847	$209.28	$209.30	$209.30
7 purchase totals =	$964.55		$1,049.8962	$1,049.89	$1,049.95	$1,049.90