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	$117.96	13.164%	$133.4883	$133.49	$133.50	$133.50
Purchase #2	$18.53	12.244%	$20.7988	$20.80	$20.80	$20.80
Purchase #3	$118.57	3.855%	$123.1409	$123.14	$123.15	$123.10
Purchase #4	$149.55	10.779%	$165.67	$165.67	$165.65	$165.70
Purchase #5	$103.59	9.643%	$113.5792	$113.58	$113.60	$113.60
Purchase #6	$144.86	4.804%	$151.8191	$151.82	$151.80	$151.80
Purchase #7	$115.66	11.441%	$128.8927	$128.89	$128.90	$128.90
7 purchase totals =	$768.72		$837.3890	$837.39	$837.40	$837.40