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	$174.27	4.147%	$181.497	$181.50	$181.50	$181.50
Purchase #2	$98.36	10.119%	$108.313	$108.31	$108.30	$108.30
Purchase #3	$179.50	4.712%	$187.958	$187.96	$187.95	$188.00
Purchase #4	$122.45	3.166%	$126.3268	$126.33	$126.35	$126.30
Purchase #5	$117.54	11.868%	$131.4896	$131.49	$131.50	$131.50
Purchase #6	$137.30	9.842%	$150.8131	$150.81	$150.80	$150.80
Purchase #7	$171.35	9.714%	$187.9949	$187.99	$188.00	$188.00
7 purchase totals =	$1,000.77		$1,074.3924	$1,074.39	$1,074.40	$1,074.40