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	$136.82	11.615%	$152.7116	$152.71	$152.70	$152.70
Purchase #2	$54.35	13.539%	$61.7084	$61.71	$61.70	$61.70
Purchase #3	$148.86	13.477%	$168.9219	$168.92	$168.90	$168.90
Purchase #4	$109.47	4.556%	$114.4575	$114.46	$114.45	$114.50
Purchase #5	$85.94	9.299%	$93.9316	$93.93	$93.95	$93.90
Purchase #6	$113.43	12.285%	$127.3649	$127.36	$127.35	$127.40
Purchase #7	$129.75	9.803%	$142.4694	$142.47	$142.45	$142.50
7 purchase totals =	$778.62		$861.5653	$861.56	$861.50	$861.60