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	$187.97	5.538%	$198.3798	$198.38	$198.40	$198.40
Purchase #2	$122.41	5.239%	$128.8231	$128.82	$128.80	$128.80
Purchase #3	$93.46	11.212%	$103.9387	$103.94	$103.95	$103.90
Purchase #4	$112.60	4.289%	$117.4294	$117.43	$117.45	$117.40
Purchase #5	$136.82	7.575%	$147.1841	$147.18	$147.20	$147.20
Purchase #6	$144.45	4.398%	$150.8029	$150.80	$150.80	$150.80
Purchase #7	$213.80	11.777%	$238.9792	$238.98	$239.00	$239.00
7 purchase totals =	$1,011.51		$1,085.5372	$1,085.53	$1,085.60	$1,085.50