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	$41.87	11.284%	$46.5946	$46.59	$46.60	$46.60
Purchase #2	$162.51	13.456%	$184.3773	$184.38	$184.40	$184.40
Purchase #3	$75.48	6.287%	$80.2254	$80.23	$80.25	$80.20
Purchase #4	$233.52	7.207%	$250.3498	$250.35	$250.35	$250.30
Purchase #5	$173.71	7.869%	$187.3792	$187.38	$187.40	$187.40
Purchase #6	$6.48	5.300%	$6.8234	$6.82	$6.80	$6.80
Purchase #7	$131.66	8.446%	$142.78	$142.78	$142.80	$142.80
7 purchase totals =	$825.23		$898.5297	$898.53	$898.60	$898.50