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	$99.51	13.631%	$113.0742	$113.07	$113.05	$113.10
Purchase #2	$97.32	3.154%	$100.3895	$100.39	$100.40	$100.40
Purchase #3	$159.52	12.128%	$178.8666	$178.87	$178.85	$178.90
Purchase #4	$44.54	4.309%	$46.4592	$46.46	$46.45	$46.50
Purchase #5	$89.66	9.487%	$98.166	$98.17	$98.15	$98.20
Purchase #6	$185.41	13.458%	$210.3625	$210.36	$210.35	$210.40
Purchase #7	$232.95	10.301%	$256.9462	$256.95	$256.95	$256.90
7 purchase totals =	$908.91		$1,004.2642	$1,004.27	$1,004.20	$1,004.40