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	$124.93	4.818%	$130.9491	$130.95	$130.95	$130.90
Purchase #2	$130.72	10.782%	$144.8142	$144.81	$144.80	$144.80
Purchase #3	$186.53	11.689%	$208.3335	$208.33	$208.35	$208.30
Purchase #4	$218.78	9.248%	$239.0128	$239.01	$239.00	$239.00
Purchase #5	$112.28	10.238%	$123.7752	$123.78	$123.80	$123.80
Purchase #6	$197.88	12.653%	$222.9178	$222.92	$222.90	$222.90
Purchase #7	$109.98	6.255%	$116.8592	$116.86	$116.85	$116.90
7 purchase totals =	$1,081.10		$1,186.6618	$1,186.66	$1,186.65	$1,186.60