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	$101.62	10.630%	$112.4222	$112.42	$112.40	$112.40
Purchase #2	$203.58	6.737%	$217.2952	$217.30	$217.30	$217.30
Purchase #3	$43.67	7.404%	$46.9033	$46.90	$46.90	$46.90
Purchase #4	$168.69	4.176%	$175.7345	$175.73	$175.75	$175.70
Purchase #5	$77.56	10.390%	$85.6185	$85.62	$85.60	$85.60
Purchase #6	$195.30	8.502%	$211.9044	$211.90	$211.90	$211.90
Purchase #7	$217.52	3.232%	$224.5502	$224.55	$224.55	$224.60
7 purchase totals =	$1,007.94		$1,074.4283	$1,074.42	$1,074.40	$1,074.40