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	$181.33	12.650%	$204.2682	$204.27	$204.25	$204.30
Purchase #2	$118.96	7.184%	$127.5061	$127.51	$127.50	$127.50
Purchase #3	$127.32	11.592%	$142.0789	$142.08	$142.10	$142.10
Purchase #4	$177.76	3.412%	$183.8252	$183.83	$183.85	$183.80
Purchase #5	$81.46	9.317%	$89.0496	$89.05	$89.05	$89.00
Purchase #6	$118.94	9.365%	$130.0787	$130.08	$130.10	$130.10
Purchase #7	$123.25	3.581%	$127.6636	$127.66	$127.65	$127.70
7 purchase totals =	$929.02		$1,004.4703	$1,004.48	$1,004.50	$1,004.50